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1 september 2003 dsc-5909/17 ? 2003 integrated device technology, inc. all rights reserved. product specifications subject to change without notice. 2.5 volt high-speed terasync? fifo 18-bit/9-bit configurations 2,048 x 18/4,096 x 9, 4,096 x 18/8,192 x 9, 8,192 x 18/16,384 x 9, 16,384 x 18/32,768 x 9, 32,768 x 18/65,536 x 9, 65,536 x 18/131,072 x 9, 131,072 x 18/262,144 x 9, 262,144 x 18/524,288 x 9, 524,288 x 18/1,048,576 x 9 idt72t1845, idt72t1855 idt72t1865, idt72t1875 idt72t1885, idt72t1895 idt72t18105, idt72t18115 idt72t18125 idt and the idt logo are trademarks of integrated device technology, inc. terasync fifo is a trademark of integrated device tec hnology, inc. commercial and industrial temperature ranges features: ? ? ? ? ? choose among the following memory organizations: idt72t1845 ? ? ? ? ? 2,048 x 18/4,096 x 9 idt72t1855 ? ? ? ? ? 4,096 x 18/8,192 x 9 idt72t1865 ? ? ? ? ? 8,192 x 18/16,384 x 9 idt72t1875 ? ? ? ? ? 16,384 x 18/32,768 x 9 idt72t1885 ? ? ? ? ? 32,768 x 18/65,536 x 9 idt72t1895 ? ? ? ? ? 65,536 x 18/131,072 x 9 idt72t18105 ? ? ? ? ? 131,072 x 18/262,144 x 9 idt72t18115 ? ? ? ? ? 262,144 x 18/524,288 x 9 idt72t18125 ? ? ? ? ? 524,288 x 18/1,048,576 x 9 ? ? ? ? ? up to 225 mhz operation of clocks ? ? ? ? ? user selectable hstl/lvttl input and/or output ? ? ? ? ? read enable & read clock echo outputs aid high speed operation ? ? ? ? ? user selectable asynchronous read and/or write port timing ? ? ? ? ? 2.5v lvttl or 1.8v, 1.5v hstl port selectable input/ouput voltage ? ? ? ? ? 3.3v input tolerant ? ? ? ? ? mark & retransmit, resets read pointer to user marked position ? ? ? ? ? write chip select ( wcs ) input enables/disables write operations ? ? ? ? ? read chip select ( rcs ) synchronous to rclk ? ? ? ? ? programmable almost-empty and almost-full flags, each flag can default to one of eight preselected offsets ? ? ? ? ? program programmable flags by either serial or parallel means ? ? ? ? ? selectable synchronous/asynchronous timing modes for almost- empty and almost-full flags ? ? ? ? ? separate sclk input for serial programming of flag offsets ? ? ? ? ? user selectable input and output port bus-sizing - x9 in to x9 out - x9 in to x18 out - x18 in to x9 out - x18 in to x18 out ? ? ? ? ? big-endian/little-endian user selectable byte representation ? ? ? ? ? auto power down minimizes standby power consumption ? ? ? ? ? master reset clears entire fifo ? ? ? ? ? partial reset clears data, but retains programmable settings ? ? ? ? ? empty, full and half-full flags signal fifo status ? ? ? ? ? select idt standard timing (using ef and ff flags) or first word fall through timing (using or and ir flags) ? ? ? ? ? output enable puts data outputs into high impedance state ? ? ? ? ? jtag port, provided for boundary scan function ? ? ? ? ? available in 144-pin (13mm x 13mm) or 240-pin (19mm x 19mm) plasticball grid array (pbga) ? ? ? ? ? easily expandable in depth and width ? ? ? ? ? independent read and write clocks (permit reading and writing simultaneously) ? ? ? ? ? high-performance submicron cmos technology ? ? ? ? ? industrial temperature range (?40 c to +85 c) is available input register output register ram array 2,048 x 18 or 4,096 x 9 4,096 x 18 or 8,192 x 9 8,192 x 18 or 16,384 x 9 16,384 x 18 or 32,768 x 9 32,768 x 18 or 65,536 x 9 65,536 x 18 or 131,072 x 9 131,072 x 18 or 262,144 x 9 262,144 x 18 or 524,288 x 9 524,288 x 18 or 1,048,576 x 9 flag logic ff / ir paf ef / or pae hf read pointer read control logic write control logic write pointer reset logic wen wclk/wr d 0 -d n (x18 or x9) ld mrs ren rclk/rd oe q 0 -q n (x18 or x9) offset register prs fwft/si sen rt 5909 drw01 bus configuration control logic be ow ip pfm fsel0 fsel1 iw mark sclk rcs jtag control (boundary scan) tck tms tdo tdi trst asyr wcs erclk eren hstl i/0 control vref whstl rhstl asyw shstl functional block diagram
2 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 wcs prs ld ff / ir ow hf be ip asyr pfm eren mark wclk mrs fwft/si paf fsel0 shstl fsel1 dnc rhstl pae ef / or rclk wen whstl v ddq v ddq v ddq v cc v cc v ddq v ddq v ddq ren rt asyw sen v ddq v cc v cc gnd gnd v cc v cc v ddq rcs oe sclk vref v ddq v cc v cc v ddq q17 iw d17 v cc gnd v cc v ddq q16 d15 d16 v cc gnd v cc v ddq q15 d13 d14 v ddq v cc v ddq q14 q13 d11 d12 v ddq v cc v ddq q12 q11 d9 d10 v ddq v ddq v ddq v cc v cc v ddq v ddq v ddq q10 q9 d7 d3 d1 trst tck tdi erclk q1 q3 q5 q8 d6 d4 d2 d0 tms td0 q0 q2 q4 q6 q7 a1 ball pad corner a b c d e f g h j k l m 123456789101112 5909 drw02 gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd v cc gnd gnd gnd gnd gnd v cc gnd gnd v cc v cc gnd gnd gnd gnd d5 d8 idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895 only pbga: 1mm pitch, 13mm x 13mm (bb144-1, order code: bb) top view pin configurations note: 1. dnc - do not connect.
3 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 pin configurations (continued) idt72t18105/72t18115/72t18125 only pbga: 1mm pitch, 19mm x 19mm (bb240-1, order code: bb) top view note: 1. dnc - do not connect. a b c d e f g h j k l m n p r t d13 gnd tdo gnd d4 tms gnd d5 d10 d1 q14 gnd q0 q2 q11 q8 q3 gnd gnd gnd gnd gnd gnd gnd gnd gnd v cc v cc v cc v cc v cc v cc v cc v cc gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd v cc ren gnd paf eren v ddq oe rclk v cc v cc v cc v ddq v ddq v ddq v ddq v ddq v ddq 12 34 56 78 910111213141516 a1 ball pad corner mrs v cc v cc ff ef v cc v cc v cc dnc v cc v cc v cc v cc sen v cc v cc v cc v ddq v ddq v ddq v ddq rcs v ddq v ddq v cc v cc v cc sclk v cc v cc v cc v cc wcs v cc v cc v cc pae ld hf gnd v ddq mark v ddq rt shstl fwft/si fs0 ow ip fs1 be gnd pfm dnc asyr rhstl gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd gnd whstl asyw vref iw gnd gnd gnd gnd v cc v ddq v ddq v cc wen gnd wclk prs v cc 5909 drw02a u v v cc d16 d15 tdi tck trst d6 d0 d2 d9 d12 d14 d17 d3 q15 q16 gnd erclk q4 q13 q10 q7 q5 d11 d8 d7 gnd q6 q1 q9 q12 17 18 v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq v ddq q17 dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc dnc
4 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 description: the idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895/ 72t18105/72t18115/72t18125 are exceptionally deep, extremely high speed, cmos first-in-first-out (fifo) memories with clocked read and write controls and a flexible bus-matching x18/x9 data flow. these fifos offer several key user benefits: ? flexible x18/x9 bus-matching on both read and write ports a user selectable mark location for retransmit user selectable i/o structure for hstl or lvttl asynchronous/synchronous translation on the read or write ports the first word data latency period, from the time the first word is written to an empty fifo to the time it can be read, is fixed and short. high density offerings up to 9 mbit bus-matching terasync fifos are particularly appropriate for network, video, telecommunications, data communications and other applications that need to buffer large amounts of data and match busses of unequal sizes. each fifo has a data input port (d n ) and a data output port (q n ), both of which can assume either a 18-bit or a 9-bit width as determined by the state of external control pins input width (iw) and output width (ow) pin during the master reset cycle. the input port can be selected as either a synchronous (clocked) interface, or asynchronous interface. during synchronous operation the input port is controlled by a write clock (wclk) input and a write enable ( wen ) input. data present on the dn data inputs is written into the fifo on every rising edge of wclk when wen is asserted. during asynchronous operation only the wr input is used to write data into the fifo. data is written on a rising edge of wr, the wen input should be tied to its active state, (low). the output port can be selected as either a synchronous (clocked) interface, or asynchronous interface. during synchronous operation the output port is controlled by a read clock (rclk) input and read enable ( ren ) input. data is read from the fifo on every rising edge of rclk when ren is asserted. during asynchronous operation only the rd input is used to read data from the fifo. data is read on a rising edge of rd, the ren input should be tied to its active state, low. when asynchronous operation is selected on the output port the fifo must be configured for standard idt mode, also the rcs should be tied low and the oe input used to provide three-state control of the outputs, qn. the output port can be selected for either 2.5v lvttl or hstl operation, this operation is selected by the state of the rhstl input during a master reset. an output enable ( oe ) input is provided for three-state control of the outputs. a read chip select ( rcs ) input is also provided, the rcs input is synchronized to the read clock, and also provides three-state control of the qn data outputs. when rcs is disabled, the data outputs will be high impedance. during asynchronous operation of the output port, rcs should be enabled, held low. echo read enable, eren and echo read clock, erclk outputs are provided. these are outputs from the read port of the fifo that are required for high speed data communication, to provide tighter synchronization between the data being transmitted from the qn outputs and the data being received by the input device. data read from the read port is available on the output bus with respect to eren and erclk, this is very useful when data is being read at high speed. the erclk and eren outputs are non-functional when the read port is setup for asynchronous mode. the frequencies of both the rclk and the wclk signals may vary from 0 to f max with complete independence. there are no restrictions on the frequency of the one clock input with respect to the other. there are two possible timing modes of operation with these devices: idt standard mode and first word fall through (fwft) mode. in idt standard mode, the first word written to an empty fifo will not appear on the data output lines unless a specific read operation is performed. a read operation, which consists of activating ren and enabling a rising rclk edge, will shift the word from internal memory to the data output lines. in fwft mode, the first word written to an empty fifo is clocked directly to the data output lines after three transitions of the rclk signal. a ren does not have to be asserted for accessing the first word. however, subsequent words written to the fifo do require a low on ren for access. the state of the fwft/si input during master reset determines the timing mode in use. for applications requiring more data storage capacity than a single fifo can provide, the fwft timing mode permits depth expansion by chaining fifos in series (i.e. the data outputs of one fifo are connected to the corresponding data inputs of the next). no external logic is required. these fifos have five flag pins, ef / or (empty flag or output ready), ff / ir (full flag or input ready), hf (half-full flag), pae (programmable almost-empty flag) and paf (programmable almost-full flag). the ef and ff functions are selected in idt standard mode. the ir and or functions are selected in fwft mode. hf , pae and paf are always available for use, irrespective of timing mode. pae and paf can be programmed independently to switch at any point in memory. programmable offsets determine the flag switching threshold and can be loaded by two methods: parallel or serial. eight default offset settings are also provided, so that pae can be set to switch at a predefined number of locations from the empty boundary and the paf threshold can also be set at similar predefined values from the full boundary. the default offset values are set during master reset by the state of the fsel0, fsel1, and ld pins. for serial programming, sen together with ld on each rising edge of sclk, are used to load the offset registers via the serial input (si). for parallel programming, wen together with ld on each rising edge of wclk, are used to load the offset registers via d n . ren together with ld on each rising edge of rclk can be used to read the offsets in parallel from q n regardless of whether serial or parallel offset loading has been selected. during master reset ( mrs ) the following events occur: the read and write pointers are set to the first location of the fifo. the fwft pin selects idt standard mode or fwft mode. the partial reset ( prs ) also sets the read and write pointers to the first location of the memory. however, the timing mode, programmable flag programming method, and default or programmed offset settings existing before partial reset remain unchanged. the flags are updated according to the timing mode and offsets in effect. prs is useful for resetting a device in mid-operation, when reprogramming programmable flags would be undesirable. it is also possible to select the timing mode of the pae (programmable almost- empty flag) and paf (programmable almost-full flag) outputs. the timing modes can be set to be either asynchronous or synchronous for the pae and paf flags. if asynchronous pae / paf configuration is selected, the pae is asserted low on the low-to-high transition of rclk. pae is reset to high on the low- to-high transition of wclk. similarly, the paf is asserted low on the low- to-high transition of wclk and paf is reset to high on the low-to-high transition of rclk. if synchronous pae / paf configuration is selected , the pae is asserted and updated on the rising edge of rclk only and not wclk. similarly, paf is asserted and updated on the rising edge of wclk only and not rclk. the mode desired is configured during master reset by the state of the programmable flag mode (pfm) pin. this device includes a retransmit from mark feature that utilizes two control inputs, mark and , rt (retransmit). if the mark input is enabled with respect to the rclk, the memory location being read at that point will be marked. any subsequent retransmit operation, rt goes low, will reset the read pointer to this ?marked? location.
5 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 the device can be configured with different input and output bus widths as shown in table 1. a big-endian/little-endian data word format is provided. this function is useful when data is written into the fifo in long word format (x18) and read out of the fifo in small word (x9) format. if big-endian mode is selected, then the most significant byte (word) of the long word written into the fifo will be read out of the fifo first, followed by the least significant byte. if little-endian format is selected, then the least significant byte of the long word written into the fifo will be read out first, followed by the most significant byte. the mode desired is configured during master reset by the state of the big-endian ( be ) pin. the interspersed/non-interspersed parity (ip) bit function allows the user to select the parity bit in the word loaded into the parallel port (d 0 -dn) when programming the flag offsets. if interspersed parity mode is selected, then the fifo will assume that the parity bit is located in bit positions d 8 during the parallel programming of the flag offsets. if non-interspersed parity mode is selected, then d 8 is assumed to be a valid bit and d 16 and d 17 are ignored. ip mode is selected during master reset by the state of the ip input pin. this mode is relevant only when the input width is set to x18 mode. if, at any time, the fifo is not actively performing an operation, the chip will automatically power down. once in the power down state, the standby supply current consumption is minimized. initiating any operation (by activating control inputs) will immediately take the device out of the power down state. both an asynchronous output enable pin ( oe ) and synchronous read chip select pin ( rcs ) are provided on the fifo. the synchronous read chip select is synchronized to the rclk. both the output enable and read chip select control the output buffer of the fifo, causing the buffer to be either high impedance or low impedance. a jtag test port is provided, here the fifo has fully functional boundary scan feature, compliant with ieee 1449.1 standard test access port and boundary scan architecture. the terasync fifo has the capability of operating its ports (write and/or read) in either lvttl or hstl mode, each ports selection independent of the other. the write port selection is made via whstl and the read port selection via rhstl. an additional input shstl is also provided, this allows the user to select hstl operation for other pins on the device (not associated with the write or read ports). the idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895/ 72t18105/72t18115/72t18125 are fabricated using idt?s high speed sub- micron cmos technology.
6 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 i w ow write port width read port width l l x18 x18 l h x18 x9 h l x9 x18 h h x9 x9 table 1 bus-matching configuration modes figure 1. single device configuration signal flow diagram (x18, x9) data out (q 0 - q n ) (x18, x9) data in (d 0 - d n ) master reset ( mrs ) read clock (rclk/rd) read enable ( ren ) output enable ( oe ) empty flag/output ready ( ef / or ) programmable almost-empty ( pae ) write clock (wclk/wr) write enable ( wen ) load ( ld ) full flag/input ready ( ff / ir ) programmable almost-full ( paf ) idt 72t1845 72t1855 72t1865 72t1875 72t1885 72t1895 72t18105 72t18115 72t18125 partial reset ( prs ) first word fall through/ serial input (fwft/si) retransmit ( rt ) 5909 drw03 half-full flag ( hf ) serial enable( sen ) input width (iw) output width (ow) big-endian/little-endian ( be ) interspersed/ non-interspersed parity (ip) serial clock (sclk) mark read chip select ( rcs ) rclk echo, erclk ren echo, eren write chip select ( wcs )
7 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 pin description symbol name i/o type description asyr (1) asynchronous lvttl a high on this input during master reset will select synchronous read operation for the output port. a low read port input will select asynchronous operation. if asynchronous is selected the fifo must operate in idt standard mode. asyw (1) asynchronous lvttl a high on this input during master reset will select synchronous write operation for the input port. a low write port input will select asynchronous operation. be (1) big-endian/ lvttl during master reset, a low on be will select big-endian operation. a high on be during master reset little-endian input will select little-endian format. d 0 ?d 17 data inputs hstl-lvttl data inputs for an 18- or 9-bit bus. when in 18- or 9-bit mode, the unused input pins should be tied to gnd. input ef / or empty flag/ hstl-lvttl in the idt standard mode, the ef function is selected. ef indicates whether or not the fifo memory is empty. output ready output in fwft mode, the or function is selected. or indicates whether or not there is valid data available at the outputs. erclk rclk echo hstl-lvttl read clock echo output, only available when the read is setup for synchronous mode. output eren read enable echo hstl-lvttl read enable echo output, only available when the read is setup for synchronous mode. output ff / ir full flag/ hstl-lvttl in the idt standard mode, the ff function is selected. ff indicates whether or not the fifo memory is input ready output full. in the fwft mode, the ir function is selected. ir indicates whether or not there is space available for writing to the fifo memory. fsel0 (1) flag select bit 0 lvttl during master reset, this input along with fsel1 and the ld pin, will select the default offset values for the input programmable flags pae and paf . there are up to eight possible settings available. fsel1 (1) flag select bit 1 lvttl during master reset, this input along with fsel0 and the ld pin will select the default offset values for the input programmable flags pae and paf . there are up to eight possible settings available. fwft/ first word fall hstl-lvttl during master reset, selects first word fall through or idt standard mode. after master reset, this pin si through/serial in input functions as a serial input for loading offset registers. if asynchronous operation of the read port has been selected then the fifo must be setup in idt standard mode. hf half-full flag hstl-lvttl hf indicates whether the fifo memory is more or less than half-full. output ip (1) interspersed parity lvttl during master reset, a low on ip will select non-interspersed parity mode. a high will select intersper sed input parity mode. iw (1) input width lvttl this pin, along with ow, selects the bus width of the write port. see table 1 for bus size configuration. input ld load hstl-lvttl this is a dual purpose pin. during master reset, the state of the ld input along with fsel0 and fsel1, input determines one of eight default offset values for the pae and paf flags, along with the method by which these offset registers can be programmed, parallel or serial (see table 2). after master reset, this pin enables writing to and reading from the offset registers. this pin must be high after master reset to write or read data to/from the fifo memory. mark mark for retransmit hstl-lvttl when this pin is asserted the current location of the read pointer will be marked. any subsequent retransmit input operation will reset the read pointer to this position. mrs master reset hstl-lvttl mrs initializes the read and write pointers to zero and sets the output register to all zeroes. during master input reset, the fifo is configured for either fwft or idt standard mode, bus-matching configurations, synchronous/asynchronous operation of the read or write port, one of eight programmable flag default settings, serial or parallel programming of the offset settings, big-endian/little-endian format, zero latency timing mode, interspersed parity, and synchronous versus asynchronous programmable flag timing modes. oe output enable hstl-lvttl oe provides asynchronous three-state control of the data outputs, q n. during a master or partial reset the input oe input is the only input that provide high-impedance control of the data outputs. ow (1) output width lvttl this pin, along with iw, selects the bus width of the read port. see table 1 for bus size configuration. input pae programmable hstl-lvttl pae goes low if the number of words in the fifo memory is less than offset n, which is stored in the empty almost-empty flag output offset register. pae goes high if the number of words in the fifo memory is greater than or equal to offset n. paf programmable hstl-lvttl paf goes high if the number of free locations in the fifo memory is more than offset m, which is stored in almost-full flag output the full offset register. paf goes low if the number of free locations in the fifo memory is less than or equal to m. pfm (1) programmable lvttl during master reset, a low on pfm will select asynchronous programmable flag timing mode. a high on flag mode input pfm will select synchronous programmable flag timing mode.
8 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 prs partial reset hstl-lvttl prs initializes the read and write pointers to zero and sets the output register to all zeroes. during partial reset, input the existing mode (idt or fwft), programming method (serial or parallel), and programmable flag settings are all retained. q 0 ?q 17 data outputs hstl-lvttl data outputs for an 18- or 9-bit bus. when in 9-bit mode, any unused output pins should not be connected. output outputs are not 5v tolerant regardless of the state of oe and rcs . rclk/ read clock/ hstl-lvttl if synchronous operation of the read port has been selected, when enabled by ren , the rising edge of rclk rd read strobe input reads data from the fifo memory and offsets from the programmable registers. if ld is low, the values loaded into the offset registers is output on a rising edge of rclk. if asynchronous operation of the read port has been selected, a rising edge on rd reads data from the fifo in an asynchronous manner. ren should be tied low. rcs read chip select hstl-lvttl rcs provides synchronous control of the read port and output impedance of qn, synchronous to rclk. during input a master or partial reset the rcs input is don?t care, if oe is low the data outputs will be low-impedance regardless of rcs . ren read enable hstl-lvttl if synchronous operation of the read port has been selected, ren enables rclk for reading data from the input fifo memory and offset registers. if asynchronous operation of the read port has been selected, the ren input should be tied low. rhstl (1) read port hstl lvttl this pin is used to select hstl or 2.5v lvttl outputs for the fifo. if hstl or ehstl outputs are select input required, this input must be tied high. otherwise it should be tied low. rt retransmit hstl-lvttl rt asserted on the rising edge of rclk initializes the read pointer to zero, sets the ef flag to low ( or to high input in fwft mode) and doesn?t disturb the write pointer, programming method, existing timing mode or programmable flag settings. if a mark has been set via the mark input pin, then the read pointer will jump to the ?mark? location. sclk serial clock hstl-lvttl a rising edge on sclk will clock the serial data present on the si input into the offset registers providing that input sen is enabled. sen serial enable hstl-lvttl sen enables serial loading of programmable flag offsets. input shstl system hstl lvttl all inputs not associated with the write or read port can be selected for hstl operation via the shstl input. select input tck (2) jtag clock hstl-lvttl clock input for jtag function. one of four terminals required by ieee standard 1149.1-1990. test operations input of the device are synchronous to tck. data from tms and tdi are sampled on the rising edge of tck and outputs change on the falling edge of tck. if the jtag function is not used this signal needs to be tied to gnd. tdi (2) jtag test data hstl-lvttl one of four terminals required by ieee standard 1149.1-1990. during the jtag boundary scan operation, test input input data serially loaded via the tdi on the rising edge of tck to either the instruction register, id register and bypass register. an internal pull-up resistor forces tdi high if left unconnected. tdo (2) jtag test data hstl-lvttl one of four terminals required by ieee standard 1149.1-1990. during the jtag boundary scan operation, test output output data serially loaded output via the tdo on the falling edge of tck from either the instruction register, id register and bypass register. this output is high impedance except when shifting, while in shift-dr and shift-ir controller states. tms (2) jtag mode hstl-lvttl tms is a serial input pin. one of four terminals required by ieee standard 1149.1-1990. tms directs the select input the device through its tap controller states. an internal pull-up resistor forces tms high if left unconnected. trst (2) jtag reset hstl-lvttl trst is an asynchronous reset pin for the jtag controller. the jtag tap controller does not automatically input reset upon power-up, thus it must be reset by either this signal or by setting tms= high for five tck cycles. if the tap controller is not properly reset then the fifo outputs will always be in high-impedance. if the jtag function is used but the user does not want to use trst , then trst can be tied with mrs to ensure proper fifo operation. if the jtag function is not used then this signal needs to be tied to gnd. wen write enable hstl-lvttl when synchronous operation of the write port has been selected, wen enables wclk for writing data into input the fifo memory and offset registers. if asynchronous operation of the write port has been selected, the wen input should be tied low. wcs write chip select hstl-lvttl the wcs pin can be regarded as a second wen input, enabling/disabling write operations. input wclk/ write clock/ hstl-lvttl if synchronous operation of the write port has been selected, when enabled by wen , the rising edge of wclk wr write strobe input writes data into the fifo. if asynchronous operation of the write port has been selected, wr writes data into the fifo on a rising edge in an asynchronous manner, ( wen should be tied to its active state). pin description (continued) symbol name i/o type description
9 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 pin description (continued) notes: 1. inputs should not change state after master reset. 2. these pins are for the jtag port. please refer to pages 29-32 and figures 6-8. symbol name i/o type description whstl (1) write port hstl lvttl this pin is used to select hstl or 2.5v lvttl inputs for the fifo. if hstl inputs are required, this input must select input be tied high. otherwise it should be tied low. v cc +2.5v supply i these are v cc supply inputs and must be connected to the 2.5v supply rail. gnd ground pin i these are ground pins and must be connected to the gnd rail. vref reference i this is a voltage reference input and must be connected to a voltage level determined from the table, voltage ?recommended dc operating conditions?. this provides the reference voltage when using hstl class inputs. if hstl class inputs are not being used, this pin should be tied low. v ddq o/p rail voltage i this pin should be tied to the desired voltage rail for providing power to the output drivers.
10 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 symbol rating commercial unit v term terminal voltage ?0.5 to +3.6 (2) v with respect to gnd t stg storage temperature ?55 to +125 c i out dc output current ?50 to +50 ma symbol parameter min. typ. max. unit v cc supply voltage 2.375 2.5 2.625 v gnd supply voltage 0 0 0 v v ih input high voltage ? lvttl 1.7 ? 3.45 v ? ehstl v ref +0.2 ? v ddq +0.3 v ? hstl v ref +0.2 ? v ddq +0.3 v v il input low voltage ? lvttl -0.3 ? 0.7 v ? ehstl -0.3 ? v ref -0.2 v ? hstl -0.3 ? v ref -0.2 v v ref (1) voltage reference input ? ehstl 0.8 0.9 1.0 v ? hstl 0.68 0.75 0.9 v t a operating temperature commercial 0 ? 70 c t a operating temperature industrial -40 ? 85 c absolute maximum ratings recommended dc operating conditions notes: 1. stresses greater than those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect reliability. 2. compliant with jedec jesd8-5. v cc terminal only. note: 1. v ref is only required for hstl or ehstl inputs. v ref should be tied low for lvttl operation. 2. outputs are not 3.3v tolerant. symbol parameter (1) conditions max. unit c in (2,3) input v in = 0v 10 (3) pf capacitance c out (1,2) output v out = 0v 10 pf capacitance capacitance (t a = +25 c, f = 1.0mhz) notes: 1. with output deselected, ( oe v ih ). 2. characterized values, not currently tested. 3. c in for vref is 20pf.
11 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 dc electrical characteristics (commercial: v cc = 2.5v 0.125v, t a = 0 c to +70 c;industrial: v cc = 2.5v 0.125v, t a = -40 c to +85 c) symbol parameter min. max. unit i li input leakage current ?10 10 a i lo output leakage current ?10 10 a v oh (5) output logic ?1? voltage, i oh = ?8 ma @v ddq = 2.5v 0.125v (lvttl) v ddq -0.4 ? v i oh = ?8 ma @v ddq = 1.8v 0.1v (ehstl) v ddq -0.4 ? v i oh = ?8 ma @v ddq = 1.5v 0.1v (hstl) v ddq -0.4 ? v v ol output logic ?0? voltage, i ol = 8 ma @v ddq = 2.5v 0.125v (lvttl) ? 0.4v v i ol = 8 ma @v ddq = 1.8v 0.1v (ehstl) ? 0.4v v i ol = 8 ma @v ddq = 1.5v 0.1v (hstl) ? 0.4v v idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895 i cc1 (1,2) active v cc current (v cc = 2.5v) i/o = lvttl ? 40 ma i/o = hstl ? 60 ma i/o = ehstl ? 60 ma i cc2 (1) standby v cc current (v cc = 2.5v) i/o = lvttl ? 10 ma i/o = hstl ? 50 ma i/o = ehstl ? 50 ma idt72t18105/72t18115/72t18125 i cc1 (1,2) active v cc current (v cc = 2.5v) i/o = lvttl ? 50 ma i/o = hstl ? 70 ma i/o = ehstl ? 70 ma i cc2 (1) standby v cc current (v cc = 2.5v) i/o = lvttl ? 20 ma i/o = hstl ? 60 ma i/o = ehstl ? 60 ma notes: 1. both wclk and rclk toggling at 20mhz. data inputs toggling at 10mhz. wcs = high, ren or rcs = high. 2. for the idt72t18105/72t18115/72t18125, typical i cc1 calculation (with data outputs in low-impedance) : for lvttl i/o i cc1 (ma) = 1.0 x fs, fs = wclk = rclk frequency (in mhz) for hstl or ehstl i/o i cc1 (ma) = 30 + (1.0 x fs), fs = wclk = rclk frequency (in mhz) for the idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895, typical i cc1 calculation (with data outputs in low-impedance) : for lvttl i/o i cc1 (ma) = 0.7ma x fs, fs = wclk = rclk frequency (in mhz) for hstl or ehstl i/o i cc1 (ma) = 30 + (0.7 x fs), fs = wclk = rclk frequency (in mhz). 3. for all devices, typical i ddq calculation: with data outputs in high-impedance: i ddq (ma) = 0.15 x fs, fs = wclk = rclk frequency (in mhz) with data outputs in low-impedance: i ddq (ma) = (c l x v ddq x fs x n)/2000 fs = wclk = rclk frequency (in mhz), v ddq = 2.5v for lvttl; 1.5v for hstl; 1.8v for ehstl, c l = capacitive load (pf), t a = 25c, n= number of outputs switching. 4. total power consumed: pt = (v cc x i cc ) + v ddq x i ddq ). 5. outputs are not 3.3v tolerant.
12 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 ac electrical characteristics (1) ? synchronous timing (commercial: v cc = 2.5v 5%, t a = 0 c to +70 c;industrial: v cc = 2.5v 5%, t a = -40 c to +85 c) notes: 1. all ac timings apply to both standard idt mode and first word fall through mode. 2. industrial temperature range product for the 5ns speed grade is available as a standard device. all other speed grades are av ailable by special order. 3. pulse widths less than minimum values are not allowed. 4. values guaranteed by design, not currently tested. commercial com?l & ind?l (2) commercial commercial idt72t1845l4-4 idt72t1845l5 idt72t1845l6-7 idt72t1845l10 idt72t1855l4-4 idt72t1855l5 idt72t1855l6-7 idt72t1855l10 idt72t1865l4-4 idt72t1865l5 idt72t1865l6-7 idt72t1865l10 idt72t1875l4-4 idt72t1875l5 idt72t1875l6-7 idt72t1875l10 idt72t1885l4-4 idt72t1885l5 idt72t1885l6-7 idt72t1885l10 idt72t1895l4-4 idt72t1895l5 idt72t1895l6-7 idt72t1895l10 idt72t18105l4-4 idt72t18105l5 idt72t18105l6-7 idt72t18105l10 idt72t18115l4-4 idt72t18115l5 idt72t18115l6-7 idt72t18115l10 idt72t18125l4-4 idt72t18125l5 idt72t18125l6-7 idt72t18125l10 symbol parameter min. max. min. max. min. max. min. max. unit f c clock cycle frequency (synchronous) ? 225 ? 200 ? 150 ? 100 mhz t a data access time 0.6 3.4 0.6 3.6 0.6 3.8 0.6 4.5 ns t clk clock cycle time 4.44 ? 5 ? 6.7 ? 10 ? ns t clkh clock high time 2.0 ? 2.3 ? 2.8 ? 4.5 ? ns t clkl clock low time 2.0 ? 2.3 ? 2.8 ? 4.5 ? ns t ds data setup time 1.2 ? 1.5 ? 2.0 ? 3.0 ? ns t dh data hold time 0.5 ? 0.5 ? 0.5 ? 0.5 ? ns t ens enable setup time 1.2 ? 1.5 ? 2.0 ? 3.0 ? ns t enh enable hold time 0.5 ? 0.5 ? 0.5 ? 0.5 ? ns t lds load setup time 1.2 ? 1.5 ? 2.0 ? 3.0 ? ns t ldh load hold time 0.5 ? 0.5 ? 0.5 ? 0.5 ? ns t wcss wcs setup time 1.2 ? 1.5 ? 2.0 ? 3.0 ? ns t wcsh wcs hold time 0.5 ? 0.5 ? 0.5 ? 0.5 ? ns f s clock cycle frequency (sclk) ? 10 ? 10 ? 10 ? 10 mhz t sclk serial clock cycle 100 ? 100 ? 100 ? 100 ? ns t sckh serial clock high 45 ? 45 ? 45 ? 45 ? ns t sckl serial clock low 45 ? 45 ? 45 ? 45 ? ns t sds serial data in setup 15 ? 15 ? 15 ? 15 ? ns t sdh serial data in hold 5 ? 5 ? 5 ? 5 ? ns t sens serial enable setup 5 ? 5 ? 5 ? 5 ? ns t senh serial enable hold 5 ? 5 ? 5 ? 5 ? ns t rs reset pulse width (3) 30 ? 30 ? 30 ? 30 ? ns t rss reset setup time 15 ? 15 ? 15 ? 15 ? ns t hrss hstl reset setup time 4 ? 4 ? 4 ? 4 ? s t rsr reset recovery time 10 ? 10 ? 10 ? 10 ? ns t rsf reset to flag and output time ? 10 ? 12 ? 15 ? 15 ns t wff write clock to ff or ir ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t ref read clock to ef or or ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t pafs write clock to synchronous programmable almost-full flag ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t paes read clock to synchronous programmable almost-empty flag ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t erclk rclk to echo rclk output ? 3.8 ? 4 ? 4.3 ? 5 ns t clken rclk to echo ren output ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t rcslz rclk to active from high-z (4) ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t rcshz rclk to high-z (4) ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t skew1 skew time between rclk and wclk for ef / or and ff / ir 3.5?4?5?7?ns t skew2 skew time between rclk and wclk for pae and paf 4?5?6?8?ns
13 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 ac electrical characteristics ? asynchronous timing (commercial: v cc = 2.5v 5%, t a = 0 c to +70 c;industrial: v cc = 2.5v 5%, t a = -40 c to +85 c) commercial com?l & ind?l (2) commercial commercial idt72t1845l4-4 idt72t1845l5 idt72t1845l6-7 idt72t1845l10 idt72t1855l4-4 idt72t1855l5 idt72t1855l6-7 idt72t1855l10 idt72t1865l4-4 idt72t1865l5 idt72t1865l6-7 idt72t1865l10 idt72t1875l4-4 idt72t1875l5 idt72t1875l6-7 idt72t1875l10 idt72t1885l4-4 idt72t1885l5 idt72t1885l6-7 idt72t1885l10 idt72t1895l4-4 idt72t1895l5 idt72t1895l6-7 idt72t1895l10 idt72t18105l4-4 idt72t18105l5 idt72t18105l6-7 idt72t18105l10 idt72t18115l4-4 idt72t18115l5 idt72t18115l6-7 idt72t18115l10 idt72t18125l4-4 idt72t18125l5 idt72t18125l6-7 idt72t18125l10 symbol parameter min. max. min. max. min. max. min. max. unit f a cycle frequency (asynchronous) ? 100 ? 83 ? 66 ? 50 mhz t aa data access time 0.6 8 0.6 10 0.6 12 0.6 14 ns t cyc cycle time 10 ? 12 ? 15 ? 20 ? ns t cyh cycle high time 4.5 ? 5 ? 7 ? 8 ? ns t cyl cycle low time 4.5 ? 5 ? 7 ? 8 ? ns t rpe read pulse after ef high 8 ? 10 ? 12 ? 14 ? ns t ffa clock to asynchronous ff ?8?10?12?14ns t efa clock to asynchronous ef ?8?10?12?14ns t pafa clock to asynchronous programmable almost-full flag ? 8 ? 10 ? 12 ? 14 ns t paea clock to asynchronous programmable almost-empty flag ? 8 ? 10 ? 12 ? 14 ns t olz output enable to output in low z (3) 0?0?0?0?ns t oe output enable to output valid ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t ohz output enable to output in high z (3) ? 3.4 ? 3.6 ? 3.8 ? 4.5 ns t hf clock to hf ?8?10?12?14ns notes: 1. all ac timings apply to both standard idt mode and first word fall through mode. 2. industrial temperature range product for the 5ns speed grade is available as a standard device. all other speed grades are av ailable by special order. 3. values guaranteed by design, not currently tested.
14 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 input pulse levels 0.25 to 1.25v input rise/fall times 0.4ns input timing reference levels 0.75 output reference levels v ddq /2 hstl 1.5v ac test conditions figure 2b. lumped capacitive load, typical derating ac test loads figure 2a. ac test load input pulse levels 0.4 to 1.4v input rise/fall times 0.4ns input timing reference levels 0.9 output reference levels v ddq /2 extended hstl 1.8v ac test conditions input pulse levels gnd to 2.5v input rise/fall times 1ns input timing reference levels v cc /2 output reference levels v ddq /2 2.5v lvttl 2.5v ac test conditions 5909 drw04 50 ? v ddq /2 i/o z 0 = 50 ? 5909 drw04a 6 5 4 3 2 1 20 30 50 80 100 200 ca p acitance (p f ) t cd (typical, ns) note: 1. v ddq = 1.5v. note: 1. v ddq = 1.8v. note: 1. for lvttl v cc = v ddq .
15 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 output enable & disable timing v ih oe v il t oe & t olz v cc 2 v cc 2 100mv 100mv t ohz 100mv 100mv output normally low output normally high v ol v oh v cc 2 v cc 2 5909 drw04b output enable output disable read chip select enable & disable timing v ih rcs v il t ens t enh t rcslz rclk v cc 2 v cc 2 100mv 100mv t rcshz 100mv 100mv output normally low output normally high v ol v oh v cc 2 v cc 2 5909 drw04c notes: 1. ren is high. 2. rcs is low. notes: 1. ren is high. 2. oe is low.
16 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 functional description timing modes: idt standard vs first word fall through (fwft) mode the idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895/ 72t18105/72t18115/72t18125 support two different timing modes of opera- tion: idt standard mode or first word fall through (fwft) mode. the selection of which mode will operate is determined during master reset, by the state of the fwft/si input. if, at the time of master reset, fwft/si is low, then idt standard mode will be selected. this mode uses the empty flag ( ef ) to indicate whether or not there are any words present in the fifo. it also uses the full flag function ( ff ) to indicate whether or not the fifo has any free space for writing. in idt standard mode, every word read from the fifo, including the first, must be requested using the read enable ( ren ) and rclk. if, at the time of master reset, fwft/si is high, then fwft mode will be selected. this mode uses output ready ( or ) to indicate whether or not there is valid data at the data outputs (q n) . it also uses input ready ( ir ) to indicate whether or not the fifo has any free space for writing. in the fwft mode, the first word written to an empty fifo goes directly to q n after three rclk rising edges, ren = low is not necessary. subsequent words must be accessed using the read enable ( ren ) and rclk. various signals, both input and output signals operate differently depending on which timing mode is in effect. idt standard mode in this mode, the status flags, ff , paf , hf , pae , and ef operate in the manner outlined in table 3. to write data into to the fifo, write enable ( wen ) must be low. data presented to the data in lines will be clocked into the fifo on subsequent transitions of the write clock (wclk). after the first write is performed, the empty flag ( ef ) will go high. subsequent writes will continue to fill up the fifo. the programmable almost-empty flag ( pae ) will go high after n + 1 words have been loaded into the fifo, where n is the empty offset value. the default setting for these values are stated in the footnote of table 2. this parameter is also user programmable. see section on programmable flag offset loading. if one continued to write data into the fifo, and we assumed no read operations were taking place, the half-full flag ( hf ) would toggle to low once (d/2 + 1) words were written into the fifo. if x18 input or x18 output bus width is selected, (d/2 + 1) = the 1,025th word for the idt72t1845, 2,049th word for idt72t1855, 4,097th word for the idt72t1865, 8,193rd word for the idt72t1875, 16,385th word for the idt72t1885, 32,769th word for the idt72t1895, 65,537th word for the idt72t18105, 131,073rd word for the idt72t18115 and 262,145th word for the idt72t18125. if both x9 input and x9 output bus widths are selected, (d/2 + 1) = the 2,049th word for the idt72t1845, 4,097th word for idt72t1855, 8,193rd word for the idt72t1865, 16,385th word for the idt72t1875, 32,769th word for the idt72t1885, 65,537th word for the idt72t1895, 131,073rd word for the idt72t18105, 262,145th word for the idt72t18115 and 524,289th word for the idt72t18125. continuing to write data into the fifo will cause the programmable almost-full flag ( paf ) to go low. again, if no reads are performed, the paf will go low after (d-m) writes to the fifo. if x18 input or x18 output bus width is selected, (d-m) = (2,048-m) writes for the idt72t1845, (4,096-m) writes for the idt72t1855, (8,192-m) writes for the idt72t1865, (16,384-m) writes for the idt72t1875, (32,768-m) writes for the idt72t1885, (65,536-m) writes for the idt72t1895, (131,072-m) writes for the idt72t18105, (262,144-m) writes for the idt72t18115 and (524,288-m) writes for the idt72t18125. if both x9 input and x9 output bus widths are selected, (d-m) = (4,096-m) writes for the idt72t1845, (8,192-m) writes for the idt72t1855, (16,384-m) writes for the idt72t1865, (32,768-m) writes for the idt72t1875, (65,536-m) writes for the idt72t1885, (131,072-m) writes for the idt72t1895, (262,144-m) writes for the idt72t18105, (524,288-m) writes for the idt72t18115 and (1,048,576-m) writes for the idt72t18125. the offset ?m? is the full offset value. the default setting for these values are stated in the footnote of table 2. this parameter is also user programmable. see section on programmable flag offset loading. when the fifo is full, the full flag ( ff ) will go low, inhibiting further write operations. if no reads are performed after a reset, ff will go low after d writes to the fifo. if the x18 input or x18 output bus width is selected, d = 2,048 writes for the idt72t1845, 4,096 writes for the idt72t1855, 8,192 writes for the idt72t1865, 16,384 writes for the idt72t1875, 32,768 writes for the idt72t1885, 65,536 writes for the idt72t1895, 131,072 writes for the idt72t18105, 262,144 writes for the idt72t18115 and 524,288 writes for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,096 writes for the idt72t1845, 8,192 writes for the idt72t1855, 16,384 writes for the idt72t1865, 32,768 writes for the idt72t1875, 65,536 writes for the idt72t1885, 131,072 writes for the idt72t1895, 262,144 writes for the idt72t18105, 524,288 writes for the idt72t18115 and 1,048,576 writes for the idt72t18125, respectively. if the fifo is full, the first read operation will cause ff to go high. subsequent read operations will cause paf and hf to go high at the conditions described in table 3. if further read operations occur, without write operations, pae will go low when there are n words in the fifo, where n is the empty offset value. continuing read operations will cause the fifo to become empty. when the last word has been read from the fifo, the ef will go low inhibiting further read operations. ren is ignored when the fifo is empty. when configured in idt standard mode, the ef and ff outputs are double register-buffered outputs. relevant timing diagrams for idt standard mode can be found in figure 11, 12, 13 and 18. first word fall through mode (fwft) in this mode, the status flags, ir , paf , hf , pae , and or operate in the manner outlined in table 4. to write data into to the fifo, wen must be low. data presented to the data in lines will be clocked into the fifo on subsequent transitions of wclk. after the first write is performed, the output ready ( or ) flag will go low. subsequent writes will continue to fill up the fifo. pae will go high after n + 2 words have been loaded into the fifo, where n is the empty offset value. the default setting for these values are stated in the footnote of table 2. this parameter is also user programmable. see section on program- mable flag offset loading. if one continued to write data into the fifo, and we assumed no read operations were taking place, the hf would toggle to low once the (d/2 + 2) words were written into the fifo. if x18 input or x18 output bus width is selected, (d/2 + 2) = the 1,026th word for the idt72t1845, 2,050th word for idt72t1855, 4,098th word for the idt72t1865, 8,194th word for the idt72t1875, 16,386th word for the idt72t1885, 32,770th word for the idt72t1895, 65,538th word for the idt72t18105, 131,074th word for the idt72t18115 and 262,146th word for the idt72t18125. if both x9 input and x9 output bus widths are selected, (d/2 + 2) = the 2,050th word for the idt72t1845, 4,098th word for idt72t1855, 8,194th word for the idt72t1865, 16,386th word for the idt72t1875, 32,770th word for the idt72t1885, 65,538th word for the idt72t1895, 131,074th word for the idt72t18105, 262,146th word for the idt72t18115 and 524,290th word for the idt72t18125. continuing to write data into the fifo will cause the paf to go low. again, if no reads are performed, the paf will go low after (d-m) writes to the fifo. if x18 input or x18 output bus width is selected, (d-m) = (2,049-m) writes for the idt72t1845,
17 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,097 writes for the idt72t1845, 8,193 writes for the idt72t1855, 16,385 writes for the idt72t1865, 32,769 writes for the idt72t1875, 65,537 writes for the idt72t1885, 131,073 writes for the idt72t1895, 262,145 writes for the idt72t18105, 524,289 writes for the idt72t18115 and 1,048,577 writes for the idt72t18125, respectively. note that the additional word in fwft mode is due to the capacity of the memory plus output register. if the fifo is full, the first read operation will cause the ir flag to go low. subsequent read operations will cause the paf and hf to go high at the conditions described in table 4. if further read operations occur, without write operations, the pae will go low when there are n + 1 words in the fifo, where n is the empty offset value. continuing read operations will cause the fifo to become empty. when the last word has been read from the fifo, or will go high inhibiting further read operations. ren is ignored when the fifo is empty. when configured in fwft mode, the or flag output is triple register- buffered, and the ir flag output is double register-buffered. relevant timing diagrams for fwft mode can be found in figure 14, 15, 16 and 19. programming flag offsets full and empty flag offset values are user programmable. the idt72t1845/ 72t1855/72t1865/72t1875/72t1885/72t1895/72t18105/72t18115/ 72t18125 have internal registers for these offsets. there are eight default offset values selectable during master reset. these offset values are shown in table 2. offset values can also be programmed into the fifo in one of two ways; serial or parallel loading method. the selection of the loading method is done using the ld (load) pin. during master reset, the state of the ld input determines whether serial or parallel flag offset programming is enabled. a high on ld during master reset selects serial loading of offset values. a low on ld during master reset selects parallel loading of offset values. in addition to loading offset values into the fifo, it is also possible to read the current offset values. offset values can be read via the parallel output port q 0 -qn, regardless of the programming mode selected (serial or parallel). it is not possible to read the offset values in serial fashion. figure 3, programmable flag offset programming sequence , summaries the control pins and sequence for both serial and parallel programming modes. for a more detailed description, see discussion that follows. the offset registers may be programmed (and reprogrammed) any time after master reset, regardless of whether serial or parallel programming has been selected. valid programming ranges are from 0 to d-1. synchronous vs asynchronous programmable flag timing selection the idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895/ 72t18105/72t18115/72t18125 can be configured during the master reset cycle with either synchronous or asynchronous timing for paf and pae flags by use of the pfm pin. if synchronous paf / pae configuration is selected (pfm, high during mrs ), the paf is asserted and updated on the rising edge of wclk only and not rclk. similarly, pae is asserted and updated on the rising edge of rclk only and not wclk. for detail timing diagrams, see figure 23 for synchronous paf timing and figure 24 for synchronous pae timing. if asynchronous paf / pae configuration is selected (pfm, low during mrs ), the paf is asserted low on the low-to-high transition of wclk and paf is reset to high on the low-to-high transition of rclk. similarly, pae is asserted low on the low-to-high transition of rclk. pae is reset to high on the low-to-high transition of wclk. for detail timing diagrams, see figure 25 for asynchronous paf timing and figure 26 for asynchronous pae timing. (4,097-m) writes for the idt72t1855, (8,193-m) writes for the idt72t1865, (16,385-m) writes for the idt72t1875, (32,769-m) writes for the idt72t1885, (65,536-m) writes for the idt72t1895, (131,073-m) writes for the idt72t18105, (262,145-m) writes for the idt72t18115 and (524,289-m) writes for the idt72t18125. if both x9 input and x9 output bus widths are selected, (d-m) = (4,097-m) writes for the idt72t1845, (8,193-m) writes for the idt72t1855, (16,385-m) writes for the idt72t1865, (32,769-m) writes for the idt72t1875, (65,537-m) writes for the idt72t1885, (131,073-m) writes for the idt72t1895, (262,145-m) writes for the idt72t18105, (524,289-m) writes for the idt72t18115 and (1,048,577-m) writes for the idt72t18125. the offset m is the full offset value. the default setting for these values are stated in the footnote of table 2. when the fifo is full, the input ready ( ir ) flag will go high, inhibiting further write operations. if no reads are performed after a reset, ir will go high after d writes to the fifo. if x18 input or x18 output bus width is selected, d = 2,049 writes for the idt72t1845, 4,097 writes for the idt72t1855, 8,193 writes for the idt72t1865, 16,385 writes for the idt72t1875, 32,769 writes for the idt72t1885, 65,536 writes for the idt72t1895, 131,073 writes for the idt72t18105, 262,145 writes for the idt72t18115 and 524,289 writes for the table 2 default programmable flag offsets notes: 1. n = empty offset for pae . 2. m = full offset for paf . 3. as well as selecting serial programming mode, one of the default values will also be loaded depending on the state of fsel0 & fsel1. 4. as well as selecting parallel programming mode, one of the default values will also be loaded depending on the state of fsel0 & fsel1. idt72t1845 offsets n,m all other x9 to x9 * ld fsel1 fsel0 m odes mode lhl 511 511 l l h 255 255 l l l 127 127 lhh 63 63 h l l 31 1,023 hhl 15 31 hlh 7 15 hhh 3 7 idt72t1855, 72t1865, 72t1875, 72t1885, 72t1895, 72t18105, 72t18115, 72t18125 * ld fsel1 fsel0 offsets n,m h l l 1,023 lhl 511 l l h 255 lll 127 lhh 63 hhl 31 hlh 15 hhh 7 * ld fsel1 fsel0 program mode h x x serial (3) l x x parallel (4) * this pin must be high after master reset to write or read data to/from the fifo memory.
18 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 0 1 to n (1) (n+1) to 1,024 1,025 to (2048-(m+1)) (2048-m) to 2,047 2,048 0 1 to n (1) (n+1) to 2,048 2,049 to (4,096-(m+1)) (4,096-m) to 4,095 4,096 table 3 ? status flags for idt standard mode table 4 ? status flags for fwft mode f f p a f h f p a e e f hh hl l hh hl h hh h hh hhl hh h l lhh ll lhh 5909 drw05 i r p a f h f p a e o r lh hl h lh hl l lh h hl lhlhl l l lhl hl lhl number of words in fifo iw = x18 or ow = x18 iw = ow = x9 idt72t18105 idt72t1895 idt72t18115 idt72t18125 0 1 to n+1 (1) (n+2) to 32,769 32,770 to (65,537-(m+1)) (65,537-m) to 65,536 65,537 0 (n+2) to 65,537 65,538 to (131,073-(m+1)) (131,073-m) to 131,072 131,073 0 (n+2) to 131,073 131,074 to (262,145-(m+1)) 262,145 (262,145-m) to 262,144 idt72t18105 idt72t18115 idt72t18125 idt72t1895 idt72t1885 0 (n+2) to 262,145 262,146 to (524,289-(m+1)) (524,289-m) to 524,288 524,289 0 (n+2) to 524,289 524,290 to (1,048,577-(m+1)) 1,048,577 (1,048,577-m) to 1,048,576 1 to n+1 (1) 1 to n+1 (1) 1 to n+1 (1) 1 to n+1 (1) 0 1 to n (1) (n+1) to 4,096 4,097 to (8,192-(m+1)) (8,192-m) to 8,191 8,192 0 1 to n ( 1) (n+1) to 8,192 8,193 to (16,384-(m+1)) (16,384-m) to 16,383 16,384 number of words in fifo idt72t1855 iw = x18 or ow = x18 iw = ow = x9 idt72t1855 idt72t1845 idt72t1865 idt72t1875 idt72t1865 idt72t1875 idt72t1845 idt72t1885 0 1 to n (1) (n+1) to 16,384 16,385 to (32,768-(m+1)) (32,768-m) to 32,767 32,768 f f p a f h f p a e e f hh hll hh hl h hh h hh hhlhh h l lhh ll lhh number of words in fifo iw = x18 or ow = x18 iw = ow = x9 idt72t18105 idt72t1895 idt72t18115 idt72t18125 0 1 to n (1) (n+1) to 32,768 32,769 to (65,536-(m+1)) (65,536-m) to 65,535 65,536 0 1 to n (1) (n+1) to 65,536 65,537 to (131,072-(m+1)) (131,072-m) to 131,071 131,072 0 1 to n (1) (n+1) to 131,072 131,073 to (262,144-(m+1)) 262,144 (262,144-m) to 262,143 idt72t18105 idt72t18115 idt72t18125 idt72t1895 idt72t1885 0 1 to n (1) (n+1) to 262,144 262,145 to (524,288-(m+1)) (524,288-m) to 524,287 524,288 0 1 to n (1) (n+1) to 524,288 524,289 to (1,048,576-(m+1)) 1,048,576 (1,048,576-m) to 1,048,575 0 (n+2) to 1,025 1,026 to (2049-(m+1)) (2049-m) to 2,048 2,049 0 (n+2) to 2,049 2,050 to (4,097-(m+1)) (4,097-m) to 4,096 4,097 i r p a f h f p a e o r lh hlh lh hl l lh h hl lhlhl l l lhl hl lhl 0 (n+2) to 4,097 4,098 to (8,193-(m+1)) (8,193-m) to 8,192 8,193 0 (n+2) to 8,193 8,194 to (16,385-(m+1)) (16,385-m) to 16,384 16,385 number of words in fifo idt72t1855 iw = x18 or ow = x18 iw = ow = x9 idt72t1855 idt72t1845 idt72t1865 idt72t1875 idt72t1865 idt72t1875 idt72t1845 idt72t1885 0 (n+2) to 16,385 16,386 to (32,769-(m+1)) (32,769-m) to 32,768 32,769 1 to n+1 (1) 1 to n+1 (1) 1 to n+1 (1) 1 to n+1 (1) 1 to n+1 (1) note: 1. see table 2 for values for n, m. note: 1. see table 2 for values for n, m. 2. number of words in fifo = depth + output register.
19 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 3. programmable flag offset programming sequence wclk rclk x x xx x x xx ld 0 0 x 1 1 1 0 wen 0 1 1 0 x 1 1 ren 1 0 1 x 0 1 1x sen 1 1 1 x x x 0 no operation write memory read memory no operation parallel write to registers: serial shift into registers: ending with full offset (msb) i dt72t1845, idt72t1855 idt72t1865, idt72t1875 idt72t1885, idt72t1895 idt72t18105, i dt72t18115 idt72t18125 24 bits for the idt72t1845 26 bits for the idt72t1855 28 bits for the idt72t1865 30 bits for the idt72t1875 32 bits for the idt72t1885 34 bits for the idt72t1895 36 bits for the idt72t18105 38 bits for the idt72t18115 40 bits for the idt72t18125 1 bit for each rising sclk edge starting with empty offset (lsb) serial shift into registers: ending with full offset (msb) 22 bits for the idt72t1845 24 bits for the idt72t1855 26 bits for the idt72t1865 28 bits for the idt72t1875 30 bits for the idt72t1885 32 bits for the idt72t1895 34 bits for the idt72t18105 36 bits for the idt72t18115 38 bits for the idt72t18125 1 bit for each rising sclk edge starting with empty offset (lsb) x9 to x9 mode all other modes 5909 drw06 x18 input empty offset full offset x18 input (72t18105/115/125) empty offset (lsb) empty offset (msb) full offset (lsb) full offset (msb) x9 input empty offset (lsb) empty offset (msb) full offset (lsb) full offset (msb) x9 input (72t1895/105/115/125) empty offset (lsb) empty offset empty offset (msb) full offset (lsb) full offset full offset (msb) parallel read from registers: x18 input empty offset full offset x18 input (72t18105/115/125) empty offset (lsb) empty offset (msb) full offset (lsb) full offset (msb) x9 input empty offset (lsb) empty offset (msb) full offset (lsb) full offset (msb) x9 input (72t1895/105/115/125) empty offset (lsb) empty offset empty offset (msb) full offset (lsb) full offset full offset (msb) notes: 1. the programming method can only be selected at master reset. 2. parallel reading of the offset registers is always permitted regardless of which programming method has been selected. 3. the programming sequence applies to both idt standard and fwft modes.
20 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 3. programmable flag offset programming sequence (continued) x9 to x9 mode all other modes # of bits used: 12 bits for the idt72t1845 13 bits for the idt72t1855 14 bits for the idt72t1865 15 bits for the idt72t1875 16 bits for the idt72t1885 17 bits for the idt72t1895 18 bits for the idt72t18105 19 bits for the idt72t18115 20 bits for the idt72t18125 note: all unused bits of the lsb & msb are don?t care # of bits used: note: all unused bits of the lsb & msb are don?t care 11 bits for the idt72t1845 12 bits for the idt72t1855 13 bits for the idt72t1865 14 bits for the idt72t1875 15 bits for the idt72t1885 16 bits for the idt72t1895 17 bits for the idt72t18105 18 bits for the idt72t18115 19 bits for the idt72t18125 d/q8 d/q0 empty offset register 1 2 3 4 5 6 7 8 1st parallel offset write/read cycle 2nd parallel offset write/read cycle 3rd parallel offset write/read cycle 4th parallel offset write/read cycle d/q8 d/q0 empty offset register 9 10 11 12 13 14 15 16 d/q8 d/q0 full offset register 1 2 3 4 5 6 7 8 d/q8 d/q0 empty offset register 17 5th parallel offset write/read cycle d/q8 d/q0 full offset register 9 10 11 12 13 14 15 16 6th parallel offset write/read cycle d/q8 d/q0 17 full offset register idt72t1895/72t18105/72t18115/72t18125 (1) ? x9 bus width d/q8 d/q0 empty offset register 1 2 3 4 5 6 7 8 1st parallel offset write/read cycle 2nd parallel offset write/read cycle 3rd parallel offset write/read cycle d/q8 d/q0 empty offset register 9 10 11 12 13 14 15 16 d/q8 d/q0 full offset register 1 2 3 4 5 6 7 8 4th parallel offset write/read cycle d/q8 d/q0 full offset register 9 10 11 12 13 14 15 16 idt72t1845/72t1855/72t1865/72t1875/ 72t1885/72t1895 (1) ? x9 bus width d/q17 d/q0 d/q16 empty offset register data inputs/outputs # of bits used 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1st parallel offset write/read cycle data inputs/outputs 2nd parallel offset write/read cycle 1 2 3 4 5 6 7 8 10 11 12 13 14 15 9 full offset register 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 10 11 12 13 14 15 9 non-interspersed parity interspersed parity d/q17 d/q0 d/q16 d/q8 d/q8 16 16 idt72t1845/72t1855/72t1865/72t1875/ 72t1885/72t1895 ? x18 bus width 4666 drw 06 d/q17 d/q0 d/q16 empty offset (lsb) register data inputs/outputs # of bits used 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 empty offset (msb) register data inputs/outputs 17 16 18 1st parallel offset write/read cycle 2nd parallel offset write/read cycle data inputs/outputs data inputs/outputs 3rd parallel offset write/read cycle 4th parallel offset write/read cycle 1 2 3 4 5 6 7 8 10 11 12 13 14 15 9 18 17 full offset (lsb) register 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 10 11 12 13 14 15 9 full offset (msb) register 17 18 18 17 non-interspersed parity interspersed parity d/q17 d/q0 d/q16 d/q17 d/q0 d/q16 d/q17 d/q0 d/q16 d/q8 d/q8 16 16 idt 72t18105/72t18115/72t18125 ? x18 bus width 5909 drw07 19 19 19 19 18 19 20 18 19 20 notes: 1. when programming the idt72t1895 with an input bus width of x9 and output bus width of x18, 4 write cycles will be required. w hen reading the idt72t1895 with an output bus width of x9 and input bus width of x18, 4 read cycles will be required. a total of 6 program/read cycles will be required i f both the input and output bus widths are set to x9. 2. consecutive reads of the offset registers is not permitted. the read operation must be disabled for a minimum of one rclk cyc le in between offset register accesses. (please refer to figure 22, parallel read of programmable flag registers (idt standard and fwft modes) for more details).
21 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 serial programming mode if serial programming mode has been selected, as described above, then programming of pae and paf values can be achieved by using a combination of the ld , sen , sclk and si input pins. programming pae and paf proceeds as follows: when ld and sen are set low, data on the si input are written, one bit for each sclk rising edge, starting with the empty offset lsb and ending with the full offset msb. if x9 to x9 mode is selected, a total of 24 bits for the idt72t1845, 26 bits for the idt72t1855, 28 bits for the idt72t1865, 30 bits for the idt72t1875, 32 bits for the idt72t1885, 34 bits for the idt72t1895, 36 bits for the idt72t18105, 38 bits for the idt72t18115 and 40 bits for the idt72t18125. for any other mode of operation (that includes x18 bus width on either the input or output), minus 2 bits from the values above. so, a total of 22 bits for the idt72t1845, 24 bits for the idt72t1855, 26 bits for the idt72t1865, 28 bits for the idt72t1875, 30 bits for the idt72t1885, 32 bits for the idt72t1895, 34 bits for the idt72t18105, 36 bits for the idt72t18115 and 38 bits for the idt72t18125. see figure 20, serial loading of program- mable flag registers , for the timing diagram for this mode. using the serial method, individual registers cannot be programmed selectively. pae and paf can show a valid status only after the complete set of bits (for all offset registers) has been entered. the registers can be reprogrammed as long as the complete set of new offset bits is entered. when ld is low and sen is high, no serial write to the registers can occur. write operations to the fifo are allowed before and during the serial programming sequence. in this case, the programming of all offset bits does not have to occur at once. a select number of bits can be written to the si input and then, by bringing ld and sen high, data can be written to fifo memory via d n by toggling wen . when wen is brought high with ld and sen restored to a low, the next offset bit in sequence is written to the registers via si. if an interruption of serial programming is desired, it is sufficient either to set ld low and deactivate sen or to set sen low and deactivate ld . once ld and sen are both restored to a low level, serial offset programming continues. from the time serial programming has begun, neither programmable flag will be valid until the full set of bits required to fill all the offset registers has been written. measuring from the rising sclk edge that achieves the above criteria; paf will be valid after three more rising wclk edges plus t paf , pae will be valid after the next three rising rclk edges plus t pae . it is only possible to read the flag offset values via the parallel output port qn. parallel mode if parallel programming mode has been selected, as described above, then programming of pae and paf values can be achieved by using a combination of the ld , wclk , wen and d n input pins. if the fifo is configured for an input bus width and output bus width both set to x9, then the total number of write operations required to program the offset registers is 4 for the idt72t1845/ 72t1855/72t1865/72t1875/72t1885 or 6 for the idt72t1895/72t18105/ 72t18115/72t18125. refer to figure 3, programmable flag offset pro- gramming sequence, for a detailed diagram of the data input lines d 0 -dn used during parallel programming. if the fifo is configured for an input to output bus width of x9 to x18, x18 to x9 or x18 to x18, then the following number of write operations are required. for an input bus width of x18 a total of 2 write operations will be required to program the offset registers for the idt72t1845/72t1855/ 72t1865/72t1875/72t1885/72t1895 or 4 for the idt72t18105/72t18115/ 72t18125. for an input bus width of x9 a total of 4 write operations will be required to program the offset registers for the idt72t1845/72t1855/72t1865/ 72t1875/72t1885. a total of 6 will be required for the idt72t1895/72t18105/ 72t18115/72t18125. refer to figure 3, programmable flag offset pro- gramming sequence, for a detailed diagram. for example, programming pae and paf on the idt72t1895 configured for x18 bus width proceeds as follows: when ld and wen are set low, data on the inputs dn are written into the lsb of the empty offset register on the first low-to-high transition of wclk. upon the second low-to-high transition of wclk, data are written into the msb of the empty offset register. on the third low-to-high transition of wclk, data are written into the lsb of the full offset register. on the fourth low-to-high transition of wclk, data are written into the msb of the full offset register. the fifth low-to-high transition of wclk, data are written, once again to the empty offset register. note that for x9 bus width, one extra write cycle is required for both the empty offset register and full offset register. see figure 21, parallel loading of programmable flag registers , for the timing diagram for this mode. the act of writing offsets in parallel employs a dedicated write offset register pointer. the act of reading offsets employs a dedicated read offset register pointer. the two pointers operate independently; however, a read and a write should not be performed simultaneously to the offset registers. a master reset initializes both pointers to the empty offset (lsb) register. a partial reset has no effect on the position of these pointers. write operations to the fifo are allowed before and during the parallel programming sequence. in this case, the programming of all offset registers does not have to occur at one time. one, two or more offset registers can be written and then by bringing ld high, write operations can be redirected to the fifo memory. when ld is set low again, and wen is low, the next offset register in sequence is written to. as an alternative to holding wen low and toggling ld , parallel programming can also be interrupted by setting ld low and toggling wen . note that the status of a programmable flag ( pae or paf ) output is invalid during the programming process. from the time parallel programming has begun, a programmable flag output will not be valid until the appropriate offset word has been written to the register(s) pertaining to that flag. measuring from the rising wclk edge that achieves the above criteria; paf will be valid after two more rising wclk edges plus t paf , pae will be valid after the next two rising rclk edges plus t pae plus t skew2 . the act of reading the offset registers employs a dedicated read offset register pointer. the contents of the offset registers can be read on the q 0 -q n pins when ld is set low and ren is set low. it is important to note that consecutive reads of the offset registers is not permitted. the read operation must be disabled for a minimum of one rclk cycle in between offset register accesses. if the fifo is configured for an input bus width and output bus width both set to x9, then the total number of read operations required to read the offset registers is 4 for the idt72t1845/72t1855/72t1865/72t1875/72t1885 or 6 for the idt72t1895/72t18105/72t18115/72t18125. refer to figure 3, programmable flag offset programming sequence, for a detailed diagram of the data input lines d 0 -dn used during parallel programming. if the fifo is configured for an input to output bus width of x9 to x18, x18 to x9 or x18 to x18, then the following number of read operations are required: for an output bus width of x18 a total of 2 read operations will be required to read the offset registers for the idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895 or 4 for the idt72t18105/72t18115/72t18125. for an output bus width of x9 a total of 4 read operations will be required to read the offset registers for the idt72t1845/72t1855/72t1865/72t1875/72t1885. a total of 6 will be re- quired for the idt72t1895/72t18105/72t18115/72t18125. refer to figure 3, programmable flag offset programming sequence, for a detailed diagram. see figure 22, parallel read of programmable flag registers , for the timing diagram for this mode. it is permissible to interrupt the offset register read sequence with reads or writes to the fifo. the interruption is accomplished by deasserting ren , ld ,
22 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 or both together. when ren and ld are restored to a low level, reading of the offset registers continues where it left off. it should be noted, and care should be taken from the fact that when a parallel read of the flag offsets is performed, the data word that was present on the output lines qn will be overwritten. parallel reading of the offset registers is always permitted regardless of which timing mode (idt standard or fwft modes) has been selected. retransmit from mark operation the retransmit from mark feature allows fifo data to be read repeatedly starting at a user-selected position. the fifo is first put into retransmit mode that will ?mark? a beginning word and also set a pointer that will prevent ongoing fifo write operations from over-writing retransmit data. the retransmit data can be read repeatedly any number of times from the ?marked? position. the fifo can be taken out of retransmit mode at any time to allow normal device operation. the ?mark? position can be selected any number of times, each selection over- writing the previous mark location. retransmit operation is available in both idt standard and fwft modes. during idt standard mode the fifo is put into retransmit mode by a low- to-high transition on rclk when the ?mark? input is high and ef is high. the rising rclk edge ?marks? the data present in the fifo output register as the first retransmit data. the fifo remains in retransmit mode until a rising edge on rclk occurs while mark is low. once a ?marked? location has been set (and the device is still in retransmit mode, mark is high), a retransmit can be initiated by a rising edge on rclk while the retransmit input ( rt ) is low. ren must be high (reads disabled) before bringing rt low. the device indicates the start of retransmit setup by setting ef low, also preventing reads. when ef goes high, retransmit setup is complete and read operations may begin starting with the first data at the mark location. since idt standard mode is selected, every word read including the first ?marked? word following a retransmit setup requires a low on ren (read enabled). note, write operations may continue as normal during all retransmit functions, however write operations to the ?marked? location will be prevented. see figure 18, retransmit from mark (idt standard mode) , for the relevant timing diagram. during fwft mode the fifo is put into retransmit mode by a rising rclk edge when the ?mark? input is high and or is low. the rising rclk edge ?marks? the data present in the fifo output register as the first retransmit data. the fifo remains in retransmit mode until a rising rclk edge occurs while mark is low. once a marked location has been set (and the device is still in retransmit can be initiated by a rising rclk edge while the retransmit input ( rt ) is low. ren must be high (reads disabled) before bringing rt low. the device indicates the start of retransmit setup by setting or high. when or goes low, retransmit setup is complete and on the next rising rclk edge after retransmit setup is complete, ( rt goes high), the contents of the first retransmit location are loaded onto the output register. since fwft mode is selected, the first word appears on the outputs regardless of ren , a low on ren is not required for the first word. reading all subsequent words requires a low on ren to enable the rising rclk edge. see figure 19, retransmit from mark timing (fwft mode) , for the relevant timing diagram. note, for the idt72t1845/72t1855/72t1865/72t1875/72t1885/ 72t1895 there must be a minimum of 32 bytes of data between the write pointer and read pointer when the mark is asserted, for the idt72t18105/72t18115 there must be a minimum of 128 bytes and for the idt72t18125 there must be a minimum of 256 bytes. remember, 2(x9) bytes = 1(x18) word. (32 bytes = 16 word = 8 long words). also, once the mark is set, the write pointer will not increment past the ?marked? location until the mark is deasserted. this prevents ?overwriting? of retransmit data. hstl/lvttl i/o both the write port and read port are user selectable between hstl or lvttl i/o, via two select pins, whstl and rhstl respectively. all other control pins are selectable via shstl, see table 5 for details of groupings. note, that when the write port is selected for hstl mode, the user can reduce the power consumption (in stand-by mode by utilizing the wcs input). all ?static pins? must be tied to vcc or gnd. these pins are lvttl only, and are purely device configuration pins. table 5 i/o configuration whstl select rhstl select shstl select static pins whstl: high = hstl rhstl: high = hstl shstl: high = hstl lvttl only low = lvttl low = lvttl low = lvttl dn (i/p) rclk/rd (i/p) ef / or (o/p) sclk (i/p) prs (i/p) iw (i/p) ow (i/p) wclk/wr (i/p) rcs (i/p) paf (o/p) ld (i/p) trst (i/p) bm (i/p) asyw (i/p) wen (i/p) mark (i/p) eren (o/p) mrs (i/p) tdi (i/p) asyr (i/p) be (i/p) wcs (i/p) ren (i/p) pae (o/p) tck (i/p) ip (i/p) fsel0 (i/p) oe (i/p) ff / ir (o/p) tms (i/p) fsel1 (i/p) pfm (i/p) rt (i/p) hf (o/p) sen (i/p) shstl (i/p) whstl (i/p) qn (o/p) erclk (o/p) fwft/si (i/p) rhstl (i/p) tdo (o/p)
23 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 signal description inputs: data in (d 0 - d n ) data inputs for 18-bit wide data (d 0 - d 17 ) or data inputs for 9-bit wide data (d 0 - d 8 ). controls: master reset ( mrs ) a master reset is accomplished whenever the mrs input is taken to a low state. this operation sets the internal read and write pointers to the first location of the ram array. pae will go low, paf will go high, and hf will go high. if fwft/si is low during master reset then the idt standard mode, along with ef and ff are selected. ef will go low and ff will go high. if fwft/si is high, then the first word fall through mode (fwft), along with ir and or , are selected. or will go high and ir will go low. all control settings such as ow, iw, be , rm, pfm and ip are defined during the master reset cycle. during a master reset, the output register is initialized to all zeroes. a master reset is required after power up, before a write operation can take place. mrs is asynchronous. see figure 9, master reset timing , for the relevant timing diagram. partial reset ( prs ) a partial reset is accomplished whenever the prs input is taken to a low state. as in the case of the master reset, the internal read and write pointers are set to the first location of the ram array, pae goes low, paf goes high, and hf goes high. whichever mode is active at the time of partial reset, idt standard mode or first word fall through, that mode will remain selected. if the idt standard mode is active, then ff will go high and ef will go low. if the first word fall through mode is active, then or will go high, and ir will go low. following partial reset, all values held in the offset registers remain unchanged. the programming method (parallel or serial) currently active at the time of partial reset is also retained. the output register is initialized to all zeroes. prs is asynchronous. a partial reset is useful for resetting the device during the course of operation, when reprogramming programmable flag offset settings may not be convenient. see figure 10, partial reset timing , for the relevant timing diagram. asynchronous write ( asyw ) the write port can be configured for either synchronous or asynchronous mode of operation. if during master reset the asyw input is low, then asynchronous operation of the write port will be selected. during asynchro- nous operation of the write port the wclk input becomes wr input, this is the asynchronous write strobe input. a rising edge on wr will write data present on the dn inputs into the fifo. ( wen must be tied low when using the write port in asynchronous mode). when the write port is configured for asynchronous operation the full flag ( ff ) operates in an asynchronous manner, that is, the full flag will be updated based in both a write operation and read operation. note, if asynchronous mode is selected, fwft is not permissable. refer to figures 30, 31, 34 and 35 for relevant timing and operational waveforms. asynchronous read ( asyr ) the read port can be configured for either synchronous or asynchronous mode of operation. if during a master reset the asyr input is low, then asynchronous operation of the read port will be selected. during asynchro- nous operation of the read port the rclk input becomes rd input, this is the asynchronous read strobe input. a rising edge on rd will read data from the fifo via the output register and qn port. ( ren must be tied low during asynchronous operation of the read port). the oe input provides three-state control of the qn output bus, in an asynchronous manner. ( rcs , provides three-state control of the read port in synchronous mode). when the read port is configured for asynchronous operation the device must be operating on idt standard mode, fwft mode is not permissible if the read port is asynchronous. the empty flag ( ef ) operates in an asynchronous manner, that is, the empty flag will be updated based on both a read operation and a write operation. refer to figures 32, 33, 34 and 35 for relevant timing and operational waveforms. retransmit ( rt ) the retransmit ( rt ) input is used in conjunction with the mark input, together they provide a means by which data previously read out of the fifo can be reread any number of times. if retransmit operation has been selected (i.e. the mark input is high), a rising edge on rclk while rt is low will reset the read pointer back to the memory location set by the user via the mark input. if idt standard mode has been selected the ef flag will go low and remain low for the time that rt is held low. rt can be held low for any number of rclk cycles, the read pointer being reset to the marked location. the next rising edge of rclk after rt has returned high, will cause ef to go high, allowing read operations to be performed on the fifo. the next read operation will access data from the ?marked? memory location. subsequent retransmit operations may be performed, each time the read pointer returning to the ?marked? location. see figure 18, retransmit from mark (idt standard mode) for the relevant timing diagram. if fwft mode has been selected the or flag will go high and remain high for the time that rt is held low. rt can be held low for any number of rclk cycles, the read pointer being reset to the ?marked? location. the next rclk rising edge after rt has returned high, will cause or to go low and due to fwft operation, the contents of the marked memory location will be loaded onto the output register, a read operation being required for all subsequent data reads. subsequent retransmit operations may be performed each time the read pointer returning to the ?marked? location. see figure 19, retransmit from mark (fwft mode) for the relevant timing diagram. mark the mark input is used to select retransmit mode of operation. an rclk rising edge while mark is high will mark the memory location of the data currently present on the output register, the device will also be placed into retransmit mode. note, for the idt72t1845/72t1855/72t1865/72t1875/ 72t1885/72t1895 there must be a minimum of 32 bytes of data between the write pointer and read pointer when the mark is asserted, for the idt72t18105/ 72t18115 there must be a minimum of 128 bytes and for the idt72t18125 there must be a minimum of 256 bytes. remember, 2(x9) bytes = 1(x18) word. (32 bytes = 16 word = 8 long words). also, once the mark is set, the write pointer will not increment past the ?marked? location until the mark is deasserted. this prevents ?overwriting? of retransmit data.
24 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 the mark input must remain high during the whole period of retransmit mode, a falling edge of rclk while mark is low will take the device out of retransmit mode and into normal mode. any number of mark locations can be set during fifo operation, only the last marked location taking effect. once a mark location has been set the write pointer cannot be incremented past this marked location. during retransmit mode write operations to the device may continue without hindrance. first word fall through/serial in ( fwft/si ) this is a dual purpose pin. during master reset, the state of the fwft/ si input determines whether the device will operate in idt standard mode or first word fall through (fwft) mode. if, at the time of master reset, fwft/si is low, then idt standard mode will be selected. this mode uses the empty flag ( ef ) to indicate whether or not there are any words present in the fifo memory. it also uses the full flag function ( ff ) to indicate whether or not the fifo memory has any free space for writing. in idt standard mode, every word read from the fifo, including the first, must be requested using the read enable ( ren ) and rclk. if, at the time of master reset, fwft/si is high, then fwft mode will be selected. this mode uses output ready ( or ) to indicate whether or not there is valid data at the data outputs (q n) . it also uses input ready ( ir ) to indicate whether or not the fifo memory has any free space for writing. in the fwft mode, the first word written to an empty fifo goes directly to q n after three rclk rising edges, ren = low is not necessary. subsequent words must be accessed using the read enable ( ren ) and rclk. after master reset, fwft/si acts as a serial input for loading pae and paf offsets into the programmable registers. the serial input function can only be used when the serial loading method has been selected during master reset. serial programming using the fwft/si pin functions the same way in both idt standard and fwft modes. write strobe & write clock (wr/wclk) if synchronous operation of the write port has been selected via asyw , this input behaves as wclk. a write cycle is initiated on the rising edge of the wclk input. data setup and hold times must be met with respect to the low-to-high transition of the wclk. it is permissible to stop the wclk. note that while wclk is idle, the ff / ir , paf and hf flags will not be updated. (note that wclk is only capable of updating hf flag to low). the write and read clocks can either be independent or coincident. if asynchronous operation has been selected this input is wr (write strobe). data is asynchronously written into the fifo via the dn inputs whenever there is a rising edge on wr. in this mode the wen input must be tied low. write enable ( wen ) when the wen input is low, data may be loaded into the fifo ram array on the rising edge of every wclk cycle if the device is not full. data is stored in the ram array sequentially and independently of any ongoing read operation. when wen is high, no new data is written in the ram array on each wclk cycle. to prevent data overflow in the idt standard mode, ff will go low, inhibiting further write operations. upon the completion of a valid read cycle, ff will go high allowing a write to occur. the ff is updated by two wclk cycles + t skew after the rclk cycle. to prevent data overflow in the fwft mode, ir will go high, inhibiting further write operations. upon the completion of a valid read cycle, ir will go low allowing a write to occur. the ir flag is updated by two wclk cycles + t skew after the valid rclk cycle. wen is ignored when the fifo is full in either fwft or idt standard mode. if asynchronous operation of the write port has been selected, then wen must be held active, (tied low). read strobe & read clock (rd/rclk) if synchronous operation of the read port has been selected via asyr , this input behaves as rclk. a read cycle is initiated on the rising edge of the rclk input. data can be read on the outputs, on the rising edge of the rclk input. it is permissible to stop the rclk. note that while rclk is idle, the ef / or , pae and hf flags will not be updated. (note that rclk is only capable of updating the hf flag to high). the write and read clocks can be independent or coincident. if asynchronous operation has been selected this input is rd (read strobe) . data is asynchronously read from the fifo via the output register whenever there is a rising edge on rd. in this mode the ren and rcs inputs must be tied low. the oe input is used to provide asynchronous control of the three-state qn outputs. write chip select ( wcs ) the wcs disables all write port inputs (data only) if it is held high. to perform normal operations on the write port, the wcs must be enabled, held low. read enable ( ren ) when read enable is low, data is loaded from the ram array into the output register on the rising edge of every rclk cycle if the device is not empty. when the ren input is high, the output register holds the previous data and no new data is loaded into the output register. the data outputs q 0 -q n maintain the previous data value. in the idt standard mode, every word accessed at q n , including the first word written to an empty fifo, must be requested using ren provided that rcs is low. when the last word has been read from the fifo, the empty flag ( ef ) will go low, inhibiting further read operations. ren is ignored when the fifo is empty. once a write is performed, ef will go high allowing a read to occur. the ef flag is updated by two rclk cycles + t skew after the valid wclk cycle. both rcs and ren must be active, low for data to be read out on the rising edge of rclk. in the fwft mode, the first word written to an empty fifo automatically goes to the outputs q n , on the third valid low-to-high transition of rclk + t skew after the first write. ren and rcs do not need to be asserted low for the first word to fall through to the output register. in order to access all other words, a read must be executed using ren and rcs . the rclk low-to-high transition after the last word has been read from the fifo, output ready ( or ) will go high with a true read (rclk with ren = low; rcs = low), inhibiting further read operations. ren is ignored when the fifo is empty. if asynchronous operation of the read port has been selected, then ren must be held active, (tied low). serial enable ( sen ) the sen input is an enable used only for serial programming of the offset registers. the serial programming method must be selected during master reset. sen is always used in conjunction with ld . when these lines are both low, data at the si input can be loaded into the program register one bit for each low-to-high transition of sclk. when sen is high, the programmable registers retains the previous settings and no offsets are loaded. sen functions the same way in both idt standard and fwft modes.
25 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 output enable ( oe ) when output enable is enabled (low), the parallel output buffers receive data from the output register. when oe is high, the output data bus (q n ) goes into a high impedance state. during master or a partial reset the oe is the only input that can place the output bus qn, into high-impedance. during reset the rcs input can be high or low, it has no effect on the qn outputs. read chip select ( rcs ) the read chip select input provides synchronous control of the read output port. when rcs goes low, the next rising edge of rclk causes the qn outputs to go to the low-impedance state. when rcs goes high, the next rclk rising edge causes the qn outputs to return to high z. during a master or partial reset the rcs input has no effect on the qn output bus, oe is the only input that provides high-impedance control of the qn outputs. if oe is low the qn data outputs will be low-impedance regardless of rcs until the first rising edge of rclk after a reset is complete. then if rcs is high the data outputs will go to high-impedance. the rcs input does not effect the operation of the flags. for example, when the first word is written to an empty fifo, the ef will still go from low to high based on a rising edge of rclk, regardless of the state of the rcs input. also, when operating the fifo in fwft mode the first word written to an empty fifo will still be clocked through to the output register based on rclk, regardless of the state of rcs . for this reason the user must take care when a data word is written to an empty fifo in fwft mode. if rcs is disabled when an empty fifo is written into, the first word will fall through to the output register, but will not be available on the qn outputs which are in high-z. the user must take rcs active low to access this first word, place the output bus in low-z. ren must remain disabled high for at least one cycle after rcs has gone low. a rising edge of rclk with rcs and ren active low, will read out the next word. care must be taken so as not to lose the first word written to an empty fifo when rcs is high. refer to figure 17, rcs and ren read operation (fwft mode). the rcs pin must also be active (low) in order to perform a retransmit. see figure 13 for read cycle and read chip select timing (idt standard mode). see figure 16 for read cycle and read chip select timing (first word fall through mode). if asynchronous operation of the read port has been selected, then rcs must be held active, (tied low). oe provides three-state control of qn. write port hstl select (whstl) the control inputs, data inputs and flag outputs associated with the write port can be setup to be either hstl or lvttl. if whstl is high during the master reset, then hstl operation of the write port will be selected. if whstl is low at master reset, then lvttl will be selected. the inputs and outputs associated with the write port are listed in table 5. read port hstl select (rhstl) the control inputs, data inputs and flag outputs associated with the read port can be setup to be either hstl or lvttl. if rhstl is high during the master reset, then hstl operation of the read port will be selected. if rhstl is low at master reset, then lvttl will be selected for the read port, then echo clock and echo read enable will not be provided. the inputs and outputs associated with the read port are listed in table 5. system hstl select (shstl) all inputs not associated with the write and read port can be setup to be either hstl or lvttl. if shstl is high during master reset, then hstl operation of all the inputs not associated with the write and read port will be selected. if shstl is low at master reset, then lvttl will be selected. the inputs associated with shstl are listed in table 5. load ( ld ) this is a dual purpose pin. during master reset, the state of the ld input, along with fsel0 and fsel1, determines one of eight default offset values for the pae and paf flags, along with the method by which these offset registers can be programmed, parallel or serial (see table 2). after master reset, ld enables write operations to and read operations from the offset registers. only the offset loading method currently selected can be used to write to the registers. offset registers can be read only in parallel. after master reset, the ld pin is used to activate the programming process of the flag offset values pae and paf . pulling ld low will begin a serial loading or parallel load or read of these offset values. this pin must be high after master reset to write or read data to/from the fifo memory. bus-matching (iw, ow) the pins iw and ow are used to define the input and output bus widths. during master reset, the state of these pins is used to configure the device bus sizes. see table 1 for control settings. all flags will operate on the word/byte size boundary as defined by the selection of bus width. see figure 5 for bus- matching byte arrangement . big-endian/little-endian ( be ) during master reset, a low on be will select big-endian operation. a high on be during master reset will select little-endian format. this function is useful when data is written into the fifo in word format (x18) and read out of the fifo in word format (x18) or byte format (x9). if big-endian mode is selected, then the most significant byte of the word written into the fifo will be read out of the fifo first, followed by the least significant byte. if little-endian format is selected, then the least significant byte of the word written into the fifo will be read out first, followed by the most significant byte. the mode desired is configured during master reset by the state of the big-endian ( be ) pin. see figure 5 for bus-matching byte arrangement . programmable flag mode (pfm) during master reset, a low on pfm will select asynchronous program- mable flag timing mode. a high on pfm will select synchronous program- mable flag timing mode. if asynchronous paf / pae configuration is selected (pfm, low during mrs ), the pae is asserted low on the low-to-high transition of rclk. pae is reset to high on the low-to-high transition of wclk. similarly, the paf is asserted low on the low-to-high transition of wclk and paf is reset to high on the low-to-high transition of rclk. if synchronous pae / paf configuration is selected (pfm, high during mrs) , the pae is asserted and updated on the rising edge of rclk only and not wclk. similarly, paf is asserted and updated on the rising edge of wclk only and not rclk. the mode desired is configured during master reset by the state of the programmable flag mode (pfm) pin. interspersed parity (ip) during master reset, a low on ip will select non-interspersed parity mode. a high will select interspersed parity mode. the ip bit function allows the user to select the parity bit in the word loaded into the parallel port (d 0 -d n ) when programming the flag offsets. if interspersed parity mode is selected, then the fifo will assume that the parity bit is located in bit position d 8 and d 17 during the parallel programming of the flag offsets, and will therefore ignore d 8 when loading the offset register in parallel mode. this is also applied to the output register when reading the value of the offset register. if interspersed parity is selected then output q 8 will be invalid. if non-interspersed parity mode is selected, then d 16 and d 17 are the parity bits and are ignored during parallel
26 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 programming of the offsets. (d 8 becomes a valid bit). additionally, output q 8 will become a valid bit when performing a read of the offset register. ip mode is selected during master reset by the state of the ip input pin. outputs: full flag ( ff / ir ) this is a dual purpose pin. in idt standard mode, the full flag ( ff ) function is selected. when the fifo is full, ff will go low, inhibiting further write operations. when ff is high, the fifo is not full. if no reads are performed after a reset (either mrs or prs ), ff will go low after d writes to the fifo. if x18 input or x18 output bus width is selected, d = 2,048 for the idt72t1845, 4,096 for the idt72t1855, 8,192 for the idt72t1865, 16,384 for the idt72t1875, 32,768 for the idt72t1885, 65,536 for the idt72t1895, 131,072 writes for the idt72t18105, 262,144 writes for the idt72t18115 and 524,288 writes for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,096 for the idt72t1845, 8,192 for the idt72t1855, 16,384 for the idt72t1865, 32,768 for the idt72t1875, 65,536 for the idt72t1885, 131,072 for the idt72t1895, 262,144 writes for the idt72t18105, 524,288 writes for the idt72t18115 and 1,048,576 writes for the idt72t18125. see figure 11, write cycle and full flag timing (idt standard mode) , for the relevant timing information. in fwft mode, the input ready ( ir ) function is selected. ir goes low when memory space is available for writing in data. when there is no longer any free space left, ir goes high, inhibiting further write operations. if no reads are performed after a reset (either mrs or prs ), ir will go high after d writes to the fifo. if x18 input or x18 output bus width is selected, d = 2,049 for the idt72t1845, 4,097 for the idt72t1855, 8,193 for the idt72t1865, 16,385 for the idt72t1875, 32,769 for the idt72t1885, 65,537 for the idt72t1895, 131,073 writes for the idt72t18105, 262,145 writes for the idt72t18115 and 524,289 writes for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,097 for the idt72t1845, 8,193 for the idt72t1855, 16,385 for the idt72t1865, 32,769 for the idt72t1875, 65,537 for the idt72t1885, 131,073 for the idt72t1895, 262,145 writes for the idt72t18105, 524,289 writes for the idt72t18115 and 1,048,577 writes for the idt72t18125. see figure 14, write timing (fwft mode) , for the relevant timing information. the ir status not only measures the contents of the fifo memory, but also counts the presence of a word in the output register. thus, in fwft mode, the total number of writes necessary to deassert ir is one greater than needed to assert ff in idt standard mode. ff / ir is synchronous and updated on the rising edge of wclk. ff / ir are double register-buffered outputs. note, when the device is in retransmit mode, this flag is a comparison of the write pointer to the ?marked? location. this differs from normal mode where this flag is a comparison of the write pointer to the read pointer. empty flag ( ef / or ) this is a dual purpose pin. in the idt standard mode, the empty flag ( ef ) function is selected. when the fifo is empty, ef will go low, inhibiting further read operations. when ef is high, the fifo is not empty. see figure 12, read cycle, empty flag and first word latency timing (idt standard mode) , for the relevant timing information. in fwft mode, the output ready ( or ) function is selected. or goes low at the same time that the first word written to an empty fifo appears valid on the outputs. or stays low after the rclk low to high transition that shifts the last word from the fifo memory to the outputs. or goes high only with a true read (rclk with ren = low). the previous data stays at the outputs, indicating the last word was read. further data reads are inhibited until or goes low again. see figure 15, read timing (fwft mode) , for the relevant timing information. ef / or is synchronous and updated on the rising edge of rclk. in idt standard mode, ef is a double register-buffered output. in fwft mode, or is a triple register-buffered output. programmable almost-full flag ( paf ) the programmable almost-full flag ( paf ) will go low when the fifo reaches the almost-full condition. in idt standard mode, if no reads are performed after reset ( mrs ), paf will go low after (d-m) words are written to the fifo. if x18 input or x18 output bus width is selected, (d-m) = (2,048-m) writes for the idt72t1845, (4,096-m) writes for the idt72t1855, (8,192-m) writes for the idt72t1865, (16,384-m) writes for the idt72t1875, (32,768-m) writes for the idt72t1885, (65,536-m) writes for the idt72t1895, (131,072-m) writes for the idt72t18105, (262,144-m) writes for the idt72t18115 and (524,288-m) writes for the idt72t18125. if both x9 input and x9 output bus widths are selected, (d-m) = (4,096-m) writes for the idt72t1845, (8,192-m) writes for the idt72t1855, (16,384-m) writes for the idt72t1865, (32,768-m) writes for the idt72t1875, (65,536-m) writes for the idt72t1885, (131,072-m) writes for the idt72t1895, (262,144-m) writes for the idt72t18105, (524,288-m) writes for the idt72t18115 and (1,048,576-m) writes for the idt72t18125. the offset ?m? is the full offset value. the default setting for this value is stated in table 2. in fwft mode, if x18 input or x18 output bus width is selected, the paf will go low after (2,049-m) writes for the idt72t1845, (4,097-m) writes for the idt72t1855, (8,193-m) writes for the idt72t1865, (16,385-m) writes for the idt72t1875, (32,769-m) writes for the idt72t1885, (65,537-m) writes for the idt72t1895, (131,073-m) writes for the idt72t18105, (262,145-m) writes for the idt72t18115 and (524,289-m) writes for the idt72t18125. if both x9 input and x9 output bus widths are selected, the paf will go low after (4,097- m) writes for the idt72t1845, (8,193-m) writes for the idt72t1855, (16,385-m) writes for the idt72t1865, (32,769-m) writes for the idt72t1875, (65,537-m) writes for the idt72t1885, (131,073-m) writes for the idt72t1895, (262,145- m) writes for the idt72t18105, (524,289-m) writes for the idt72t18115 and (1,048,577-m) writes for the idt72t18125. the offset m is the full offset value. the default setting for this value is stated in table 2. see figure 23, synchronous programmable almost-full flag timing (idt standard and fwft mode) , for the relevant timing information. if asynchronous paf configuration is selected, the paf is asserted low on the low-to-high transition of the write clock (wclk). paf is reset to high on the low-to-high transition of the read clock (rclk). if synchronous paf configuration is selected, the paf is updated on the rising edge of wclk. see figure 25 for asynchronous programmable almost-full flag timing (idt standard and fwft mode). note, when the device is in retransmit mode, this flag is a comparison of the write pointer to the ?marked? location. this differs from normal mode where this flag is a comparison of the write pointer to the read pointer. programmable almost-empty flag ( pae ) the programmable almost-empty flag ( pae ) will go low when the fifo reaches the almost-empty condition. in idt standard mode, pae will go low when there are n words or less in the fifo. the offset ?n? is the empty offset value. the default setting for this value is stated in table 2. in fwft mode, the pae will go low when there are n+1 words or less in the fifo. the default setting for this value is stated in table 2. see figure 24, synchronous programmable almost-empty flag timing (idt standard and fwft mode) , for the relevant timing information.
27 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 if asynchronous pae configuration is selected, the pae is asserted low on the low-to-high transition of the read clock (rclk). pae is reset to high on the low-to-high transition of the write clock (wclk). if synchronous pae configuration is selected, the pae is updated on the rising edge of rclk. see figure 26, asynchronous programmable almost-empty flag timing (idt standard and fwft mode) , for the relevant timing information. half-full flag ( hf ) this output indicates a half-full fifo. the rising wclk edge that fills the fifo beyond half-full sets hf low. the flag remains low until the difference between the write and read pointers becomes less than or equal to half of the total depth of the device; the rising rclk edge that accomplishes this condition sets hf high. in idt standard mode, if no reads are performed after reset ( mrs or prs ), hf will go low after (d/2 + 1) writes to the fifo. if x18 input or x18 output bus width is selected, d = 2,048 for the idt72t1845, 4,096 for the idt72t1855, 8,192 for the idt72t1865, 16,384 for the idt72t1875, 32,768 for the idt72t1885, 65,536 for the idt72t1895, 131,072 for the idt72t18105, 262,144 for the idt72t18115 and 524,288 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,096 for the idt72t1845, 8,192 for the idt72t1855, 16,384 for the idt72t1865, 32,768 for the idt72t1875, 65,536 for the idt72t1885, 131,072 for the idt72t1895, 262,144 for the idt72t18105, 524,288 for the idt72t18115 and 1,048,576 for the idt72t18125. in fwft mode, if no reads are performed after reset ( mrs or prs ), hf will go low after (d-1/2 + 2) writes to the fifo. if x18 input or x18 output bus width is selected, d = 2,049 for the idt72t1845, 4,097 for the idt72t1855, 8,193 for the idt72t1865, 16,385 for the idt72t1875, 32,769 for the idt72t1885, 65,537 for the idt72t1895, 131,073 for the idt72t18105, 262,145 for the idt72t18115 and 524,289 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,097 for the idt72t1845, 8,193 for the idt72t1855, 16,385 for the idt72t1865, 32,769 for the idt72t1875, 65,537 for the idt72t1885, 131,073 for the idt72t1895, 262,145 for the idt72t18105, 524,289 for the idt72t18115 and 1,048,577 for the idt72t18125. see figure 27, half-full flag timing (idt standard and fwft mode) , for the relevant timing information. because hf is updated by both rclk and wclk, it is considered asynchronous. echo read clock (erclk) the echo read clock output is provided in both hstl and lvttl mode, selectable via rhstl. the erclk is a free-running clock output, it will always follow the rclk input regardless of ren , rcs . the erclk output follows the rclk input with an associated delay. this delay provides the user with a more effective read clock source when reading data from the qn outputs. this is especially helpful at high speeds when variables within the device may cause changes in the data access times. these variations in access time maybe caused by ambient temperature, supply voltage, device characteristics. the erclk output also compensates for any trace length delays between the qn data outputs and receiving devices inputs. any variations effecting the data access time will also have a corresponding effect on the erclk output produced by the fifo device, therefore the erclk output level transitions should always be at the same position in time relative to the data outputs. note, that erclk is guaranteed by design to be slower than the slowest qn, data output. refer to figure 4, echo read clock and data output relationship , figure 28, echo read clock & read enable operation and figure 29, echo rclk & echo ren operation for timing information. echo read enable ( eren ) the echo read enable output is provided in both hstl and lvttl mode, selectable via rhstl. the eren output is provided to be used in conjunction with the erclk output and provides the reading device with a more effective scheme for reading data from the qn output port at high speeds. the eren output is controlled by internal logic that behaves as follows: the eren output is active low for the rclk cycle that a new word is read out of the fifo. that is, a rising edge of rclk will cause eren to go active, low if both ren and rcs are active, low and the fifo is not empty. serial clock (sclk) during serial loading of the programming flag offset registers, a rising edge on the sclk input is used to load serial data present on the si input provided that the sen input is low. data outputs (q 0 -q n ) (q 0 - q 17 ) data outputs for 18-bit wide data or (q 0 - q 8 ) data outputs for 9-bit wide data. 5909 drw08 erclk t a t d q slowest (3) rclk t erclk t erclk figure 4. echo read clock and data output relationship notes: 1. ren is low; rcs is low. 2. t erclk > t a , guaranteed by design. 3. qslowest is the data output with the slowest access time, t a . 4. time, t d is greater than zero, guaranteed by design.
28 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 d17-d9 a a b b (a) x18 input to x18 output - big endian (b) x18 input to x18 output - little endian write to fifo read from fifo byte order on input port: byte order on output port: ba read from fifo a (c) x18 input to x9 output - big endian 1st: read from fifo b 2nd: read from fifo b (d) x18 input to x9 output - little endian 1st: read from fifo a 2nd: read from fifo a (a) x9 input to x18 output - big endian 1st: write to fifo byte order on input port: b 2nd: write to fifo byte order on output port: ab read from fifo (a) x9 input to x18 output - little endian b a read from fifo 5909 drw09 b e iw ow h l h b e iw ow l h l b e iw ow h h l b e iw ow l l h b e iw ow h l l b e iw ow l l l d8-d0 q17-q9 q8-q0 q17-q9 q8-q0 q17-q9 q8-q0 q17-q9 q8-q0 q17-q9 q8-q0 q17-q9 q8-q0 d17-d9 d8-d0 d17-q9 d8-q0 q17-q9 q8-q0 q17-q9 q8-q0 figure 5. bus-matching byte arrangement
29 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 6. standard jtag timing system interface parameters parameter symbol test conditions min. max. units jtag clock input period t tck - 100 - ns jtag clock high t tckhigh -40-ns jtag clock low t tcklow -40-ns jtag clock rise time t tckrise --5 (1) ns jtag clock fall time t tckfall --5 (1) ns jtag reset t rst -50-ns jtag reset recovery t rsr -50-ns jtag ac electrical characteristics (v cc = 2.5v 5%; tcase = 0 c to +85 c) idt72t1845 idt72t1855 idt72t1865 idt72t1875 idt72t1885 idt72t1895 idt72t18105 idt72t18115 idt72t18125 parameter symbol test conditions min. max. units data output t do (1) -20ns data output hold t doh (1) 0-ns data input t ds t rise=3ns 10 - ns t dh t fall=3ns 10 - note: 1. 50pf loading on external output signals. jtag timing specification note: 1. guaranteed by design. t 4 t 3 tdo tdo tdi/ tms tck trst t do notes to diagram: t1 = t tcklow t2 = t tckhigh t3 = t tckfall t4 = t tckrise t5 = trst (reset pulse width) t6 = trsr (reset recovery) 5909 drw10 t 5 t 6 t 1 t 2 t tck t dh t ds
30 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 jtag interface five additional pins (tdi, tdo, tms, tck and trst ) are provided to support the jtag boundary scan interface. the idt72t1845/72t1855/ 72t1865/72t1875/72t1885/72t1895/72t18105/72t18115/72t18125 in- corporates the necessary tap controller and modified pad cells to implement the jtag facility. note that idt provides appropriate boundary scan description language program files for these devices. the standard jtag interface consists of four basic elements: ? test access port (tap) ? tap controller ? instruction register (ir) ? data register port (dr) the following sections provide a brief description of each element. for a complete description refer to the ieee standard test access port specification (ieee std. 1149.1-1990). the figure below shows the standard boundary-scan architecture. figure 7. boundary scan architecture test access port (tap) the tap interface is a general-purpose port that provides access to the internal of the processor. it consists of four input ports (tclk, tms, tdi, trst ) and one output port (tdo). the tap controller the tap controller is a synchronous finite state machine that responds to tms and tclk signals to generate clock and control signals to the instruction and data registers for capture and update of data. t a p tap cont- roller mux deviceid reg. boundary scan reg. bypass reg. clkdr, shiftdr updatedr tdo tdi tms tclk trst clklr, shiftlr updatelr instruction register instruction decode control signals 5909 drw11
31 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 8. tap controller state diagram test-logic reset run-test/ idle 1 0 0 select- dr-scan select- ir-scan 1 1 1 capture-ir 0 capture-dr 0 0 exit1-dr 1 pause-dr 0 exit2-dr 1 update-dr 1 exit1-ir 1 exit2-ir 1 update-ir 1 1 0 1 1 1 5909 drw12 0 shift-dr 0 0 0 shift-ir 0 0 pause-ir 0 1 input = tms 0 0 1 refer to the ieee standard test access port specification (ieee std. 1149.1) for the full state diagram all state transitions within the tap controller occur at the rising edge of the tclk pulse. the tms signal level (0 or 1) determines the state progression that occurs on each tclk rising edge. the tap controller takes precedence over the fifo memory and must be reset after power up of the device. see trst description for more details on tap controller reset. test-logic-reset all test logic is disabled in this controller state enabling the normal operation of the ic. the tap controller state machine is designed in such a way that, no matter what the initial state of the controller is, the test-logic-reset state can be entered by holding tms at high and pulsing tck five times. this is the reason why the test reset ( trst ) pin is optional. run-test-idle in this controller state, the test logic in the ic is active only if certain instructions are present. for example, if an instruction activates the self test, then it will be executed when the controller enters this state. the test logic in the ic is idles otherwise. select-dr-scan this is a controller state where the decision to enter the data path or the select-ir-scan state is made. select-ir-scan this is a controller state where the decision to enter the instruction path is made. the controller can return to the test-logic-reset state other wise. capture-ir in this controller state, the shift register bank in the instruction register parallel loads a pattern of fixed values on the rising edge of tck. the last two significant bits are always required to be ?01?. shift-ir in this controller state, the instruction register gets connected between tdi and tdo, and the captured pattern gets shifted on each rising edge of tck. the instruction available on the tdi pin is also shifted in to the instruction register. exit1-ir this is a controller state where a decision to enter either the pause- ir state or update-ir state is made. pause-ir this state is provided in order to allow the shifting of instruction register to be temporarily halted. exit2-dr this is a controller state where a decision to enter either the shift- ir state or update-ir state is made. update-ir in this controller state, the instruction in the instruction register is latched in to the latch bank of the instruction register on every falling edge of tck. this instruction also becomes the current instruction once it is latched. capture-dr in this controller state, the data is parallel loaded in to the data registers selected by the current instruction on the rising edge of tck. shift-dr, exit1-dr, pause-dr, exit2-dr and update-dr these controller states are similar to the shift-ir, exit1-ir, pause-ir, exit2-ir and update-ir states in the instruction path. notes: 1. five consecutive tck cycles with tms = 1 will reset the tap. 2. tap controller does not automatically reset upon power-up. the user must provide a reset to the tap controller (either by trst or tms). 3. tap controller must be reset before normal fifo operations can begin.
32 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 the instruction register the instruction register allows an instruction to be shifted in serially into the processor at the rising edge of tclk. the instruction is used to select the test to be performed, or the test data register to be accessed, or both. the instruction shifted into the register is latched at the completion of the shifting process when the tap controller is at update- ir state. the instruction register must contain 4 bit instruction register-based cells which can hold instruction data. these mandatory cells are located nearest the serial outputs they are the least significant bits. test data register the test data register contains three test data registers: the bypass, the boundary scan register and device id register. these registers are connected in parallel between a common serial input and a common serial data output. the following sections provide a brief description of each element. for a complete description, refer to the ieee standard test access port specification (ieee std. 1149.1-1990). test bypass register the register is used to allow test data to flow through the device from tdi to tdo. it contains a single stage shift register for a minimum length in serial path. when the bypass register is selected by an instruction, the shift register stage is set to a logic zero on the rising edge of tclk when the tap controller is in the capture-dr state. the operation of the bypass register should not have any effect on the operation of the device in response to the bypass instruction. the boundary-scan register the boundary scan register allows serial data tdi be loaded in to or read out of the processor input/output ports. the boundary scan register is a part of the ieee 1149.1-1990 standard jtag implementation. the device identification register the device identification register is a read only 32-bit register used to specify the manufacturer, part number and version of the processor to be determined through the tap in response to the idcode instruction. idt jedec id number is 0xb3. this translates to 0x33 when the parity is dropped in the 11-bit manufacturer id field. for the idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895/ 72t18105/72t18115/72t18125, the part number field contains the following values: idt72t1845/55/65/75/85/95/105/115/125 jtag device identification register 31(msb) 28 27 12 11 1 0(lsb) version (4 bits) part number (16-bit) manufacturer id (11-bit) 0x0 0x33 1 jtag instruction register the instruction register allows instruction to be serially input into the device when the tap controller is in the shift-ir state. the instruction is decoded to perform the following: ? select test data registers that may operate while the instruction is current. the other test data registers should not interfere with chip operation and the selected data register. ? define the serial test data register path that is used to shift data between tdi and tdo during data register scanning. the instruction register is a 4 bit field (i.e. ir3, ir2, ir1, ir0) to decode 16 different possible instructions. instructions are decoded as follows. hex instruction function value 0x00 extest select boundary scan register 0x02 idcode select chip identification data register 0x01 sample/preload select boundary scan register 0x03 high-impedance jtag 0x0f bypass select bypass register jtag instruction register decoding the following sections provide a brief description of each instruction. for a complete description refer to the ieee standard test access port specification (ieee std. 1149.1-1990). extest the required extest instruction places the ic into an external boundary- test mode and selects the boundary-scan register to be connected between tdi and tdo. during this instruction, the boundary-scan register is accessed to drive test data off-chip via the boundary outputs and receive test data off-chip via the boundary inputs. as such, the extest instruction is the workhorse of ieee. std 1149.1, providing for probe-less testing of solder-joint opens/shorts and of logic cluster function. idcode the optional idcode instruction allows the ic to remain in its functional mode and selects the optional device identification register to be connected between tdi and tdo. the device identification register is a 32-bit shift register containing information regarding the ic manufacturer, device type, and version code. accessing the device identification register does not interfere with the operation of the ic. also, access to the device identification register should be immediately available, via a tap data-scan operation, after power-up of the ic or after the tap has been reset using the optional trst pin or by otherwise moving to the test-logic-reset state. sample/preload the required sample/preload instruction allows the ic to remain in a normal functional mode and selects the boundary-scan register to be connected between tdi and tdo. during this instruction, the boundary-scan register can be accessed via a date scan operation, to take a sample of the functional data entering and leaving the ic. this instruction is also used to preload test data into the boundary-scan register before loading an extest instruction. device part# field idt72t1845 040e idt72t1855 040d idt72t1865 040c idt72t1875 040b idt72t1885 040a idt72t1895 0409 idt72t18105 0419 idt72t18115 0418 idt72t18125 0417
33 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 high-impedance the optional high-impedance instruction sets all outputs (including two-state as well as three-state types) of an ic to a disabled (high-impedance) state and selects the one-bit bypass register to be connected between tdi and tdo. during this instruction, data can be shifted through the bypass register from tdi to tdo without affecting the condition of the ic outputs. bypass the required bypass instruction allows the ic to remain in a normal functional mode and selects the one-bit bypass register to be connected between tdi and tdo. the bypass instruction allows serial data to be transferred through the ic from tdi to tdo without affecting the operation of the ic.
34 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 9. master reset timing 5909 drw13 rt sen t rsf t rsf oe = high oe = low pae paf , hf q 0 - q n t rsf ef / or ff / ir t rsf t rsf if fwft = high, or = high if fwft = low, ef = low if fwft = low, ff = high if fwft = high, ir = low t rss t rss pfm t hrss ip t rs mrs t rsr ren t rss fwft/si t rsr t rsr wen fsel0, fsel1 ow, iw be ld t rsr t rss whstl rhstl shstl t rss t rss t rss t rss t rss t rss t rss t hrss t hrss note: 1. during master reset the high-impedance control of the qn data outputs is provided by oe only, rcs can be high or low until the first rising edge of rclk after master reset is complete.
35 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 10. partial reset timing t rs prs t rsr ren t rss 5909 drw14 t rsr wen rt sen t rsf t rsf oe = high oe = low pae paf , hf q 0 - q n t rsf ef / or ff / ir t rsf t rsf if fwft = high, or = high if fwft = low, ef = low if fwft = low, ff = high if fwft = high, ir = low t rss t rss t rss note: 1. during partial reset the high-impedance control of the qn data outputs is provided by oe only, rcs can be high or low until the first rising edge of rclk after master reset is complete.
36 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 11. write cycle and full flag timing (idt standard mode) d 0 - d n wen rclk ren t enh t enh q 0 - q n data read next data read t skew1 (1) 5909 drw15 wclk no write 1 2 1 2 no write t wff t a t ens t ens (1) t ds t a d x t dh t clk t clkh ff rcs t ens t rcslz t wff t skew1 t clkl d x+1 t wff t wff t ds t dh figure 12. read cycle, output enable, empty flag and first data word latency (idt standard mode) 5909 drw16 d0 - dn t ds t dh d 0 d 1 t ds t dh no operation rclk ren ef t clk t clkh t clkl t enh t ref t a t olz q0 - qn oe wclk (1) t skew1 wen t ens t ens t enh 1 2 t olz no operation last word d 0 d 1 t ens t enh t ohz last word t ref t enh t ens t a t a t ref t ens t enh wcs t oe t wcss t wcsh notes: 1. t skew1 is the minimum time between a rising wclk edge and a rising rclk edge to guarantee that ef will go high (after one rclk cycle plus t ref ). if the time between the rising edge of wclk and the rising edge of rclk is less than t skew1 , then ef deassertion may be delayed one extra rclk cycle. 2. ld = high. 3. first data word latency = t skew1 + 1*t rclk + t ref. 4. rcs is low. notes: 1. t skew1 is the minimum time between a rising rclk edge and a rising wclk edge to guarantee that ff will go high (after one wclk cycle pus t wff ). if the time between the rising edge of the rclk and the rising edge of the wclk is less than t skew1 , then the ff deassertion may be delayed one extra wclk cycle. 2. ld = high, oe = low, ef = high. 3. wcs = low.
37 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 13. read cycle and read chip select (idt standard mode) rclk ren 1 2 5909 drw 17 rcs q0 - qn wclk wen dn t ens last data d x t ens t ens t ens ef t a t ref t ref t rcslz last data-1 t rcshz t rcslz t a t rcshz t skew1 (1) t enh t ens t dh t ds t enh notes: 1. t skew1 is the minimum time between a rising wclk edge and a rising rclk edge to guarantee that ef will go high (after one rclk cycle plus t ref ). if the time between the rising edge of wclk and the rising edge of rclk is less than t skew1 , then ef deassertion may be delayed one extra rclk cycle. 2. ld = high. 3. first data word latency = t skew1 + 1*t rclk + t ref. 4. oe is low.
38 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 14. write timing (first word fall through mode) notes: 1. t skew1 is the minimum time between a rising wclk edge and a rising rclk edge to guarantee that or will go low after two rclk cycles plus t ref . if the time between the rising edge of wclk and the rising edge of rclk is less than t skew1 , then or assertion may be delayed one extra rclk cycle. 2. t skew2 is the minimum time between a rising wclk edge and a rising rclk edge to guarantee that pae will go high after one rclk cycle plus t paes . if the time between the rising edge of wclk and the rising edge of rclk is less than t skew2 , then the pae deassertion may be delayed one extra rclk cycle. 3. ld = high, oe = low 4. n = pae offset, m = paf offset and d = maximum fifo depth. 5. if x18 input or x18 output bus width is selected, d=2,049 for idt72t1845, 4,097 for idt72t1855, 8,193 for idt72t1865, 16,385 for idt72t1875, 32,769 for idt72t1885, 65,537 for idt72t1895, 131,073 for idt72t18105, 262,145 for idt72t18115, 524,288 for idt72t18125. if both x9 input and x9 output bus widths are selected, d=4,097 for idt72t1845, 8,193 for idt72t1855, 16,385 for idt72t1865, 32 ,769 for idt72t1875, 65,537 for idt72t1885, 131,073 for idt72t1895, 262,144 for idt72t18105, 524,288 for idt72t18115, 1,048,576 for idt72t18125. 6. first data word latency = t skew1 + 2*t rclk + t ref. w 1 w 2 w 4 w [n +2] w [d-m-1] w [d-m-2] w [d-1] w d w [n+3] w [n+4] w [d-m] w [d-m+1] wclk wen d0 - dn rclk t dh t ds t skew1 (1) ren q0 - qn paf hf pae ir t ds t ds t ds t skew2 t a t ref or t paes t hf t pafs t wff w [d-m+2] w 1 t enh 5909 drw18 previous data in output register (2) w 3 1 2 3 1 d-1 2 +1 ] [ w d-1 +2 ] [ w 2 d-1 +3 ] [ w 2 1 2 t ens rcs t rcslz t ens
39 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 15. read timing (first word fall through mode) notes: 1. t skew1 is the minimum time between a rising rclk edge and a rising wclk edge to guarantee that ir will go low after one wclk cycle plus t wff . if the time between the rising edge of rclk and the rising edge of wclk is less than t skew1 , then the ir assertion may be delayed one extra wclk cycle. 2. t skew2 is the minimum time between a rising rclk edge and a rising wclk edge to guarantee that paf will go high after one wclk cycle plus t pafs . if the time between the rising edge of rclk and the rising edge of wclk is less than t skew2 , then the paf deassertion may be delayed one extra wclk cycle. 3. ld = high. 4. n = pae offset, m = paf offset and d = maximum fifo depth. 5. if x18 input or x18 output bus width is selected, d=2,049 for idt72t1845, 4,097 for idt72t1855, 8,193 for idt72t1865, 16,385 for idt72t1875, 32,769 for idt72t1885, 65,537 for idt72t1895, 131,073 for idt72t18105, 262,145 for idt72t18115, 524,288 for idt72t18125. if both x9 input and x9 output bus widths are selected, d=4,097 for idt72t1845, 8,193 for idt72t1855, 16,385 for idt72t1865, 32 ,769 for idt72t1875, 65,537 for idt72t1885, 131,073 for idt72t1895, 262,144 for idt72t18105, 524,288 for idt72t18115, 1,048,576 for idt72t18125. 6. rcs = low. wclk 12 wen d0 - dn rclk t ens ren q0 - qn paf hf pae ir or w 1 w 1 w 2 w 3 w m+2 w [m+3] t ohz t skew1 t enh t ds t dh t oe t a t a t a t pafs t wff t wff t ens oe t skew2 w d 5909 drw19 t paes w [d-n] w [d-n-1] t a t a t hf t ref w [d-1] w d t a w [d-n+1] w [m+4] w [d-n+2] (1) (2) t ens d-1 + 1 ] [ w 2 d-1 + 2 ] [ w 2 1
40 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 16. read cycle and read chip select timing (first word fall through mode) wclk 12 wen d0 - dn rclk ren q0 - qn paf hf pae ir or w 1 w 2 w 3 w m+2 w [m+3] t rcshz t skew1 t enh t ds t dh t a t a t pafs t wff t wff t ens rcs t skew2 w d 5909 drw20 t paes w [d-n] w [d-n-1] t a t a w [d-1] w d t a w [d-n+1] w [m+4] w [d-n+2] (1) (2) t ens 1 t ens t rcslz t ens t hf t ref d-1 + 1 ] [ w 2 d-1 + 2 ] [ w 2 t enh notes: 1. t skew1 is the minimum time between a rising rclk edge and a rising wclk edge to guarantee that ir will go low after one wclk cycle plus t wff . if the time between the rising edge of rclk and the rising edge of wclk is less than t skew1 , then the ir assertion may be delayed one extra wclk cycle. 2. t skew2 is the minimum time between a rising rclk edge and a rising wclk edge to guarantee that paf will go high after one wclk cycle plus t pafs . if the time between the rising edge of rclk and the rising edge of wclk is less than t skew2 , then the paf deassertion may be delayed one extra wclk cycle. 3. ld = high. 4. n = pae offset, m = paf offset and d = maximum fifo depth. 5. if x18 input or x18 output bus width is selected, d=2,049 for idt72t1845, 4,097 for idt72t1855, 8,193 for idt72t1865, 16,385 for idt72t1875, 32,769 for idt72t1885, 65,537 for idt72t1895, 131,073 for idt72t18105, 262,145 for idt72t18115, 524,288 for idt72t18125. if both x9 input and x9 output bus widths are selected, d=4,097 for idt72t1845, 8,193 for idt72t1855, 16,385 for idt72t1865, 32 ,769 for idt72t1875, 65,537 for idt72t1885, 131,073 for idt72t1895, 262,144 for idt72t18105, 524,288 for idt72t18115, 1,048,576 for idt72t18125. 6. oe = low.
41 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 17 . rcs and ren read operation (fwft mode) notes: 1. it is very important that the ren be held high for at least one cycle after rcs has gone low. if ren goes low on the same cycle as rcs or earlier, then word, w1 will be lost, word, w2 will be read on the output when the bus goes to low-z. 2. the 1st word will fall through to the output register regardless of ren and rcs . however, subsequent reads require that both ren and rcs be active, low. wclk rclk ren qn 12 wen 3 t ens t enh t ens t ens t ens t enh t ens t ref t ref rcs or t rcslz w1 w2 t rcshz t rcslz t a w2 t skew t ens t enh w2 dn t dh t ds t dh t ds w1 1st word falls through to o/p register on this cycle 5909 drw21 high-z
42 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 t ref t ens t enh 5909 drw22 t ens w mk-1 wclk rclk ren rt ef paf hf pae q n 12 1 t pafs t ref 2 wen t ens t a t ens w mk w mk+1 t a t a w mk+n t a w mk w mk+1 t a t ens mark t enh t ens t paes (6) t a t skew2 t hf 3 figure 18. retransmit from mark (idt standard mode) notes: 1. retransmit setup is complete when ef returns high. 2. oe = low; rcs = low. 3. rt must be high when reading from fifo. 4. once mark is set, the write pointer will not increment past the ?marked? location, preventing overwrites of retransmit data. 5. before a ?mark? can be set there must be at least 32 bytes of data between the write pointer and read pointer locations for t he idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895, 64 bytes of data for the idt72t18105/ 72t18115 and 128 bytes of data for the idt72t18125. (32 bytes = 16 words = 8 long words). 6. a transition in the pae flag may occur one rclk cycle earlier than shown, (on cycle 2).
43 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 19. retransmit from mark (first word fall through mode) t ref t ens t enh 5909 drw23 t ens w mk-1 wclk rclk ren rt or paf hf pae q n 12 1 t pafs t ref 2 wen t ens t a t ens w mk w mk+1 t a t a w mk+n t a w mk+1 w mk+2 t a t ens mark t enh t ens t paes (6) t a t skew2 t hf w mk t a 3 notes: 1. retransmit setup is complete when or returns low. 2. oe = low; rcs = low. 3. rt must be high when reading from fifo. 4. once mark is set, the write pointer will not increment past the ?marked? location, preventing overwrites of retransmit data. 5. before a ?mark? can be set there must be at least 32 bytes of data between the write pointer and read pointer locations for t he idt72t1845/72t1855/72t1865/72t1875/72t1885/72t1895, 64 bytes of data for the idt72t18105/ 72t18115 and 128 bytes of data for the idt72t18125. (32 bytes = 16 words = 8 long words). 6. a transition in the pae flag may occur one rclk cycle earlier than shown, (on cycle 2).
44 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 20. serial loading of programmable flag registers (idt standard and fwft modes) notes: 1. x9 to x9 mode: x =12 for the idt72t1845, x = 13 for the idt72t1855, x = 14 for the idt72t1865, x = 15 for the idt72t1875, x = 16 for the idt72t1885, x = 17 for the idt72t1895, x = 18 for the idt72t18105, x = 19 for the idt72t18115 and x = 20 for the idt72t18125. 2. all other modes: x=11 for the idt72t1845, x = 12 for the idt72t1855, x = 13 for the idt72t1865, x = 14 for the idt72t1875, x = 15 for the idt72t1885 and x = 16 for the idt72t1895, x = 17 for the idt72t18105, x = 18 for the idt72t18115 and x = 19 for the idt72t18125. sclk sen si 5909 drw24 ld empty offset full offset bit x (1) t sens t lds t sds t senh t lds bit x (1) bit 1 t enh t ldh t sdh t sclk t sckh t sckl bit 1 notes: 1. oe = low. 2. the timing diagram illustrates reading of offset registers with an output bus width of 18 bits. 3. the offset registers cannot be read on consecutive rclk cycles. the read must be disabled ( ren = high) for a minimum of one rclk cycle in between register accesses. figure 22. parallel read of programmable flag registers (idt standard and fwft modes) figure 21. parallel loading of programmable flag registers (idt standard and fwft modes) notes: 1. this timing diagram is based on programming with a x18 bus width. 2. overwrites previous offset value. wclk ld wen d 0 - d 17 5909 drw25 t lds t ens pae offset t ds t dh t ldh t enh t clk t clkh t clkl paf offset pae (2) offset paf (2) offset t dh t dh t dh t ds t ds t ds t ldh t enh rclk ld ren q 0 - q 17 data in output register pae offset value paf offset value 5909 drw26 t ldh t enh t clk t clkl t clkh t a t lds t ldh t lds t ldh t lds t ens t enh t ens t enh t ens t a pae offset t a
45 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 notes: 1. m = paf offset . 2. d = maximum fifo depth. in idt standard mode: if x18 input or x18 output bus width is selected, d = 2,048 for the idt72t1845, 4,096 for the idt72t1855, 8,192 for the idt72t1865, 16,384 for the idt72t1875, 32,768 for the idt72t1885, 65,536 for the idt72t1895, 131,072 for the idt72t18105, 262,144 for the idt72t18115 and 524,288 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,096 for the idt72t1845, 8,192 for the idt72t1855, 16,384 for the idt72t1865, 32,768 for t he idt72t1875, 65,536 for the idt72t1885, 131,072 for the idt72t1895, 262,144 for the idt72t18105, 524,288 for the idt72t18115 and 1,048,576 for the idt72t18125. in fwft mode: if x18 input or x18 output bus width is selected, d = 2,049 for the idt72t1845, 4,097 for the idt72t1855, 8,193 f or the idt72t1865, 16,385 for the idt72t1875, 32,769 for the idt72t1885, 65,537 for the idt72t1895, 131,073 for the idt72t18105, 262,145 for the idt72t18115 and 524,289 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,097 for the idt72t1845, 8,193 for the idt72t1855, 16,385 for the idt72t1865, 32,769 for t he idt72t1875, 65,537 for the idt72t1885, 131,073 for the idt72t1895, 262,145 for the idt72t18105, 524,289 for the idt72t18115 and 1,048,577 for the idt72t18125. 3. t skew2 is the minimum time between a rising rclk edge and a rising wclk edge to guarantee that paf will go high (after one wclk cycle plus t pafs ). if the time between the rising edge of rclk and the rising edge of wclk is less than t skew2 , then the paf deassertion time may be delayed one extra wclk cycle. 4. paf is asserted and updated on the rising edge of wclk only. 5. select this mode by setting pfm high during master reset. 6. rcs is low. figure 23. synchronous programmable almost-full flag timing (idt standard and fwft modes) wclk wen paf rclk ren 5909 drw27 1 2 12 d-(m+1) words in fifo (2) d - m words in fifo (2) d - (m +1) words in fifo (2) t enh t ens t pafs t ens t enh t clkl t skew2 (3) t pafs t clkl notes: 1. n = pae offset. 2. for idt standard mode 3. for fwft mode. 4. t skew2 is the minimum time between a rising wclk edge and a rising rclk edge to guarantee that pae will go high (after one rclk cycle plus t paes ). if the time between the rising edge of wclk and the rising edge of rclk is less than t skew2 , then the pae deassertion may be delayed one extra rclk cycle. 5. pae is asserted and updated on the rising edge of wclk only. 6. select this mode by setting pfm high during master reset. 7. rcs = low. figure 24. synchronous programmable almost-empty flag timing (idt standard and fwft modes) wclk wen pae rclk 12 12 ren 5909 drw28 n + 1 words in fifo (2) , n + 2 words in fifo (3) t ens t skew2 (4) t enh t paes n words in fifo (2) , n + 1 words in fifo (3) t paes n words in fifo (2) , n + 1 words in fifo (3) t ens t enh t clkh t clkl
46 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 notes: 1. m = paf offset. 2. d = maximum fifo depth. in idt standard mode: if x18 input or x18 output bus width is selected, d = 2,048 for the idt72t1845, 4,096 for the idt72t1855, 8,192 for the idt72t1865, 16,384 for the idt72t1875, 32,768 for the idt72t1885, 65,536 for the idt72t1895, 131,072 for the idt72t18105, 262,144 for the idt72t18115 and 524,288 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,096 for the idt72t1845, 8,192 for the idt72t1855, 16,384 for the idt72t1865, 32,768 for t he idt72t1875, 65,536 for the idt72t1885, 131,072 for the idt72t1895, 262,144 for the idt72t18105, 524,288 for the idt72t18115 and 1,048,576 for the idt72t18125. in fwft mode: if x18 input or x18 output bus width is selected, d = 2,049 for the idt72t1845, 4,097 for the idt72t1855, 8,193 f or the idt72t1865, 16,385 for the idt72t1875, 32,769 for the idt72t1885, 65,537 for the idt72t1895, 131,073 for the idt72t18105, 262,145 for the idt72t18115 and 524,289 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,097 for the idt72t1845, 8,193 for the idt72t1855, 16,385 for the idt72t1865, 32,769 for t he idt72t1875, 65,537 for the idt72t1885, 131,073 for the idt72t1895, 262,145 for the idt72t18105, 524,289 for the idt72t18115 and 1,048,577 for the idt72t18125. 3. paf is asserted to low on wclk transition and reset to high on rclk transition. 4. select this mode by setting pfm low during master reset. 5. rcs is low. figure 25. asynchronous programmable almost-full flag timing (idt standard and fwft modes) wclk wen paf d - (m + 1) words in fifo rclk t pafa ren 5909 drw29 d - m words in fifo d - (m + 1) words in fifo t ens t pafa t enh t ens t clkl t clkh notes: 1. n = pae offset. 2. for idt standard mode. 3. for fwft mode. 4. pae is asserted low on rclk transition and reset to high on wclk transition. 5. select this mode by setting pfm low during master reset. 6. rcs = low. figure 26. asynchronous programmable almost-empty flag timing (idt standard and fwft modes) wclk wen pae n words in fifo (2) , n + 1 words in fifo (3) rclk ren 5909 drw30 t paea n + 1 words in fifo (2) , n + 2 words in fifo (3) t paea t ens t ens t enh t clkl t clkh n words in fifo (2) , n + 1 words in fifo (3)
47 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 notes: 1. in idt standard mode: d = maximum fifo depth. if x18 input or x18 output bus width is selected, d = 2,048 for the idt72t1845, 4,096 for the idt72t1855, 8,192 for the idt72t1865, 16,384 for the idt72t1875, 32,768 for the idt72t1885, 65,536 for the idt72t1895, 131,072 for the idt72t18105, 262,144 for the i dt72t18115 and 524,288 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,096 for the idt72t1845, 8,192 for the idt72t1855, 16,384 for the idt72t1865, 32,768 for the idt72t1875, 65,536 for the idt72t1885, 131,072 for the idt72t1895, 262,144 for the idt72t18105, 524,288 for the idt72t18115 and 1,048,576 for the idt72t18125. 2. in fwft mode: d = maximum fifo depth. if x18 input or x18 output bus width is selected, d = 2,049 for the idt72t1845, 4,097 f or the idt72t1855, 8,193 for the idt72t1865, 16,385 for the idt72t1875, 32,769 for the idt72t1885, 65,537 for the idt72t1895, 131,073 for the idt72t18105, 262,145 for the i dt72t18115 and 524,289 for the idt72t18125. if both x9 input and x9 output bus widths are selected, d = 4,097 for the idt72t1845, 8,193 for the idt72t1855, 16,385 for the idt72t1865, 32,769 for the idt72t1875, 65,537 for the idt72t1885, 131,073 for the idt72t1895, 262,145 for the idt72t18105, 524,289 for the idt72t18115 and 1,048,577 for the idt72t18125. 3. rcs = low. figure 27. half-full flag timing (idt standard and fwft modes) wclk t ens t enh wen hf t ens t hf rclk t hf ren 5909 drw31 t clkl t clkh d/2 words in fifo (1) , [ + 1 ] words in fifo (2) d-1 2 d/2 + 1 words in fifo (1) , [ + 2 ] words in fifo (2) d/2 words in fifo (1) , [ + 1 ] words in fifo (2) d-1 2 d-1 2
48 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 28. echo read clock & read enable operation (idt standard mode only) t ens t enh t ens rcs rclk ren qn t erclk t ens 5909 drw32 erclk t enh eren t clken t clken t clken t clken t ref ef w d-4 t a t olz t ohz t a t olz t a t a last word, w d w d-3 w d-3 w d-2 w d-1 t clken t clken notes: 1. the eren output is an ?anded? function of rcs and ren and will follow these inputs provided that the fifo is not empty. if the fifo is empty, eren will go high, thus preventing any reads. 2. the eren output is synchronous to rclk.
49 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 qn o/p reg. t a t ref or 5909 drw33 t rcslz ren t ens t enh rcs t ens rclk a b c d e f g h i w n+1 wclk wen d0 - dn t skew1 t ens t ds t enh w n+2 w n+3 erclk eren t clken t clken t clken t clken w n+1 w n+2 w n+3 t a t ref w n+1 w n+2 w n+3 t a w n last word t a t a t dh t dh t dh t ds t ds 1 2 t erclk high-z figure 29. echo rclk and echo ren operation (fwft mode only) note: 1. the o/p register is the internal output register. its contents are available on the qn output bus only when rcs and oe are both active, low, that is the bus is not in high- impedance state. 2. oe is low. cycle: a&b. at this point the fifo is empty, or is high. rcs and ren are both disabled, the output bus is high-impedance. c. word wn+1 falls through to the output register, or goes active, low. rcs is high, therefore the qn outputs are high-impedance. eren goes low to indicate that a new word has been placed on the output register. d. eren goes high, no new word has been placed on the output register on this cycle. e. no operation. f. rcs is low on this cycle, therefore the qn outputs go to low-impedance and the contents of the output register (wn+1) are made ava ilable. note: in fwft mode is important to take rcs active low at least one cycle ahead of ren , this ensures the word (wn+1) currently in the output register is made available for at least one cycle. g. ren goes active low, this reads out the second word, wn+2. eren goes active low to indicate a new word has been placed into the output register. h. word wn+3 is read out, eren remains active, low indicating a new word has been read out. note: wn+3 is the last word in the fifo. i. this is the next enabled read after the last word, wn+3 has been read out. or flag goes high and eren goes high to indicate that there is no new word available.
50 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 30. asynchronous write, synchronous read, full flag operation (idt standard mode) figure 31. asynchronous write, synchronous read, empty flag operation (idt standard mode) rclk ren 5909 drw34 ff qn w 0 t a w 1 t enh t ens t ffa t ffa t ffa wr t cyh dn t ds w d t dh w d+1 t cyc rclk ren 5909 drw35 qn last word t a w 0 t enh t ens t skew wr dn w 0 t dh 1 2 t a w 1 t ref t ref ef t cyl t ds t cyh w 1 t dh t ds t cyc note: 1. oe = low, wen = low and rcs = low. note: 1. oe = low, wen = low and rcs = low.
51 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 32. synchronous write, asynchronous read, full flag (idt standard mode) figure 33. synchronous write, asynchronous read, empty flag operation (idt standard mode) wclk wen 5909 drw36 qn t skew rd dn d f 1 2 t wff t wff ff t cyl t cyh last word no write d f+1 t aa w x t aa w x+1 t cyc wclk wen 5909 drw37 qn last word in output register w 0 rd dn t efa ef t cyh t ens t enh w 0 t ds t dh t efa t aa t rpe notes: 1. oe = low, rcs = low and ren = low. 2. asynchronous read is available in idt standard mode only. notes: 1. oe = low, rcs = low and ren = low. 2. asynchronous read is available in idt standard mode only.
52 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 figure 34. asynchronous write, asynchronous read, empty flag operation (idt standard mode) figure 35. asynchronous write, asynchronous read, full flag operation (idt standard mode) 5909 drw38 qn last word in o/p register t aa w 0 t cyh wr dn w 0 t dh t aa w 1 t efa t efa ef t cyl w 1 t dh t ds rd t cyc t rpe 5909 drw39 t cyh wr dn w y t dh t ffa ff t cyl t ds w y+1 t dh t ds rd w x t aa w x+1 w x+2 qn t ffa t cyc t cyh t cyl t cyc t aa notes: 1. oe = low, wen = low, ren = low and rcs = low. 2. asynchronous read is available in idt standard mode only. notes: 1. oe = low, wen = low, ren = low and rcs = low. 2. asynchronous read is available in idt standard mode only.
53 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 write clock (wclk) m + n mn master reset ( mrs ) read clock (rclk) data out n m + n write enable ( wen ) full flag/input ready ( ff / ir ) programmable ( paf ) programmable ( pae ) empty flag/output ready ( ef / or ) #2 output enable ( oe ) read enable ( ren ) m load ( ld ) idt 72t1845 72t1855 72t1865 72t1875 72t1885 72t1895 72t18105 72t18115 72t18125 empty flag/output ready ( ef / or ) #1 partial reset ( prs ) 5909 drw40 full flag/input ready ( ff / ir ) #2 half-full flag ( hf ) first word fall through/ serial input (fwft/si) retransmit ( rt ) #1 fifo #2 gate (1) gate (1) d 0 - d m data in d m+1 - d n q 0 - qm q m+1 - q n fifo #1 idt 72t1845 72t1855 72t1865 72t1875 72t1885 72t1895 72t18105 72t18115 72t18125 read chip select ( rcs ) serial clock (sclk) optional configurations width expansion configuration word width may be increased simply by connecting together the control signals of multiple devices. status flags can be detected from any one device. the exceptions are the ef and ff functions in idt standard mode and the ir and or functions in fwft mode. because of variations in skew between rclk and wclk, it is possible for ef / ff deassertion and ir / or assertion to vary by one cycle between fifos. in idt standard mode, such problems can be avoided by creating composite flags, that is, anding ef of every fifo, and separately anding ff of every fifo. in fwft mode, composite flags can be created by oring or of every fifo, and separately oring ir of every fifo. figure 36 demonstrates a width expansion using two idt72t1845/ 72t1855/72t1865/72t1875/72t1885/72t1895/72t18105/72t18115/ 72t18125 devices. d 0 - d 17 from each device form a 36-bit wide input bus and q 0 -q 17 from each device form a 36-bit wide output bus. any word width can be attained by adding additional idt72t1845/72t1855/72t1865/72t1875/ 72t1885/72t1895/72t18105/72t18115/72t18125 devices. notes: 1. use an and gate in idt standard mode, an or gate in fwft mode. 2. do not connect any output control signals directly together. 3. fifo #1 and fifo #2 must be the same depth, but may be different word widths. figure 36. block diagram of width expansion for the x18 input or x18 output bus width: 2,048 x 36, 4,096 x 36, 8,192 x 36, 16,384 x 18, 32,768 x 18, 65,536 x 36, 131,072 x 36, 262,144 x 36 and 524,288 x 36 for both x9 input and x9 output bus widths: 4,096 x 18, 8,192 x 18, 16,384 x 18, 32,768 x 18, 65,536 x 18, 131,072 x 18, 262,14 4 x 18, 524,288 x 18 and 1,048,576 x 18
54 commercial and industrial temperature ranges idt72t1845/55/65/75/85/95/105/115/125 2.5v terasync? 18-bit/9-bit fifo 2kx18/4kx9, 4kx18/ 8kx9, 8kx18/16kx9, 16kx18/32kx9, 32kx18/64kx9, 64kx18/128kx9, 128kx18/256kx9, 256kx18/512kx9, 512kx18/1mx9 depth expansion configuration (fwft mode only) the idt72t1845 can easily be adapted to applications requiring depths greater than 2,048 when the x18 input or x18 output bus width is selected, 4,096 for the idt72t1855, 8,192 for the idt72t1865, 16,384 for the idt72t1875, 32,768 for the idt72t1885, 65,536 for the idt72t1895, 131,072 for the idt72t18105, 262,144 for the idt72t18115 and 524,288 for the idt72t18125. when both x9 input and x9 output bus widths are selected, depths greater than 4,096 can be adapted for the idt72t1845, 8,192 for the idt72t1855, 16,384 for the idt72t1865, 32,768 for the idt72t1875, 65,536 for the idt72t1885, 131,072 for the idt72t1895, 262,144 for the idt72t8105, 524,288 for the idt72t18115 and 1,048,576 for the idt72t18125. in fwft mode, the fifos can be connected in series (the data outputs of one fifo connected to the data inputs of the next) with no external logic necessary. the resulting configuration provides a total depth equivalent to the sum of the depths associated with each single fifo. figure 37 shows a depth expansion using two idt72t1845/72t1855/72t1865/72t1875/ 72t1885/72t1895/72t18105/72t18115/72t18125 devices. care should be taken to select fwft mode during master reset for all fifos in the depth expansion configuration. the first word written to an empty configuration will pass from one fifo to the next ("ripple down") until it finally appears at the outputs of the last fifo in the chain ? no read operation is necessary but the rclk of each fifo must be free-running. each time the data word appears at the outputs of one fifo, that device's or line goes low, enabling a write to the next fifo in line. for an empty expansion configuration, the amount of time it takes for or of the last fifo in the chain to go low (i.e. valid data to appear on the last fifo's outputs) after a word has been written to the first fifo is the sum of the delays for each individual fifo: (n ? 1)*(4*transfer clock) + 3*t rclk where n is the number of fifos in the expansion and t rclk is the rclk period. note that extra cycles should be added for the possibility that the t skew1 specification is not met between wclk and transfer clock, or rclk and transfer clock, for the or flag. the "ripple down" delay is only noticeable for the first word written to an empty depth expansion configuration. there will be no delay evident for subsequent words written to the configuration. the first free location created by reading from a full depth expansion configuration will "bubble up" from the last fifo to the previous one until it finally moves into the first fifo of the chain. each time a free location is created in one fifo of the chain, that fifo's ir line goes low, enabling the preceding fifo to write a word to fill it. for a full expansion configuration, the amount of time it takes for ir of the first fifo in the chain to go low after a word has been read from the last fifo is the sum of the delays for each individual fifo: (n ? 1)*(3*transfer clock) + 2 t wclk where n is the number of fifos in the expansion and t wclk is the wclk period. note that extra cycles should be added for the possibility that the t skew1 specification is not met between rclk and transfer clock, or wclk and transfer clock, for the ir flag. the transfer clock line should be tied to either wclk or rclk, whichever is faster. both these actions result in data moving, as quickly as possible, to the end of the chain and free locations to the beginning of the chain. figure 37. block diagram of depth expansion for the x18 input or x18 output bus width: 4,096 x 18, 8,192 x 18, 16,384 x 18, 32,768 x 18, 65,536 x 18, 131,072 x 18, 262,144 x 18, 524,288 x 18 and 1,048,576 x 18 for both x9 input and x9 output bus widths: 8,192 x 9, 16,384 x 9, 32,768 x 9, 65,536 x 9, 131,072 x 9, 262,144 x 9, 524,288 x 9, 1,048,576 x 9 and 2,097,152 x 9 dn input ready write enable write clock wen wclk ir data in rclk read clock rclk ren oe output enable output ready qn dn ir gnd wen wclk or ren oe qn read enable or data out transfer clock 5909 drw41 n n n fwft/si fwft/si fwft/si idt 72t1845 72t1855 72t1865 72t1875 72t1885 72t1895 72t18105 72t18115 72t18125 rcs read chip select rcs idt 72t1845 72t1855 72t1865 72t1875 72t1885 72t1895 72t18105 72t18115 72t18125
55 corporate headquarters for sales: for tech support: 6024 silver creek valley road 800-345-7015 or 408-284-8200 408-360-1753 san jose, ca 95138 fax: 408-284-2775 email: fifohelp@idt.com www.idt.com ordering information plastic ball grid array, pbga bb144-1 (72t1845/55/65/75/85/95 only) plastic ball grid array, pbga bb240-1 (72t18105/115/125 only) commercial (0 c to +70 c) industrial (-40 c to +85 c) low power 5909 drw42 commercial only commercial and industrial commercial only commercial only l idt xxxxx device type x power xx speed x package x process / temperature range blank i (1) 72t1845 2, 048 x 18/4,096 x 9 ? 2.5v terasync ? fifo 72t1855 4, 096 x 18/8,192 x 9 ? 2.5v terasync ? fifo 72t1865 8,192 x 18/16,384 x 9 ? 2.5v terasync ? fifo 72t1875 16,384 x 18/32,768 x 9 ? 2.5v terasync ? fifo 72t1885 32,768 x 18/65,536 x 9 ? 2.5v terasync ? fifo 72t1895 65,536 x 18/131,072 x 9 ? 2.5v terasync ? fifo 72t18105 131,072 x 18/262,144 x 9 ? 2.5v terasync ? fifo 72t18115 262,144 x 18/524,288 x 9 ? 2.5v terasync ? fifo 72t18125 524,288 x 18/1,048,576 x 9 ? 2.5v terasync ? fifo clock cycle time (t clk ) speed in nanoseconds bb bb 4-4 5 6-7 10 datasheet document history 05/30/2001 pg. 18. 07/09/2001 pgs. 1, 7, 8, 19, and 50. 10/17/2001 pgs. 1-6, 8, 10, 11, 13-20, 23, 24, 26, 27, 29, 34, 35, 36, 38-43, 49-51. 11/19/2001 pgs. 1, 9, 12, 38, and 39. 11/29/2001 pgs. 1, 38, and 39. 01/15/2002 pg. 40. 03/04/2002 pgs. 9, 10, 17, and 27. 06/05/2002 pgs. 9, 10, and 14. 06/27/2002 pg. 20. 02/11/2003 pgs. 8, 9, and 31. 03/03/2003 pgs. 1, 11-13, 29, and 31-33. 09/02/2003 pgs. 7, 17, and 25. note: 1. industrial temperature range product for 5ns speed grade is available as a standard device. all other speed grades are availa ble by special order.

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