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bicmos syncbififo ? 64 x 36 x 2 integrated device technology, inc. functional block diagram IDT723612 mail 1 register input register output register clka csa w/ r a ena mba port-a control logic device control rst clkb csb w/ r b enb mbb port-b control logic mbf1 3136 drw 01 mail 2 register write pointer read pointer status flag logic parity gen/check a 0 - a 35 36 64 x 36 sram parity generation parity gen/check programmable flag offset register status flag logic input register output register 64 x 36 sram parity generation read pointer pefb pgb efb aeb ffb afb odd/ even ffa afa fs0 fs1 efa aea pga pefa mbf2 write pointer fifo2 fifo1 36 36 b 0 - b 36 the idt logo is a registered trademark and sync bififo is a trademark of integrated device technology inc. commercial temperature range may 1997 1997 integrated device technology, inc. dsc-3136/4 1 features: free-running clka and clkb can be asynchronous or coincident (simultaneous reading and writing of data on a single clock edge is permitted) two independent clocked fifos (64 x 36 storage capacity each) buffering data in opposite directions mailbox bypass register for each fifo programmable almost-full and almost-empty flags microprocessor interface control logic efa , ffa , aea , and afa flags synchronized by clka ? efb , ffb , aeb , and afb flags synchronized by clkb ? passive parity checking on each port ? parity generation can be selected for each port ? low-power advanced bicmos technology ? supports clock frequencies up to 67 mhz ? fast access times of 10ns ? available in 132-pin plastic quad flat package (pqf) or space-saving 120-pin thin quad flat package (tqfp) ? industrial temperature range (-40oc to +85oc) is avail- able, tested to military electrical specifications description: the IDT723612 is a monolithic high-speed, low-power bicmos bi-directional clocked fifo memory. it supports clock frequencies up to 67 mhz and has read access times as for latest information contact idt's web site at www.idt.com or fax-on-demand at 408-492-8391.
2 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 fast as 10ns. two independent 64 x 36 dual-port sram fifos on board the chip buffer data in opposite directions. each fifo has flags to indicate empty and full conditions and two programmable flags (almost-full and almost-empty) to indicate when a selected number of words is stored in memory. communication between each port can bypass the fifos via two 36-bit mailbox registers. each mailbox register has a flag to signal when new mail has been stored. parity is checked passively on each port and may be ignored if not desired. parity generation can be selected for data read from each port. two or more devices can be used in parallel to create wider data paths. the IDT723612 is a clocked fifo, which means each port employs a synchronous interface. all data transfers through note: 1. nc - no internal connection a port are gated to the low-to-high transition of a port clock by enable signals. the clocks for each port are independent of one another and can be asynchronous or coincident. the enables for each port are arranged to provide a simple bi- directional interface between microprocessors and/or buses with synchronous control. the full flag ( ffa , ffb ) and almost-full ( afa , afb ) flag of a fifo are two-stage synchronized to the port clock that writes data to its array. the empty flag ( efa , efb ) and almost-empty ( aea , aeb ) flag of a fifo are two stage synchronized to the port clock that reads data from its array. the IDT723612 is characterized for operation from 0 c to 70 c. 2. uses yamaichi socket ic51-1324-828 pin configurations * * electrical pin 1 in center of beveled edge. pin 1 identifier in corner. gnd b 0 b 1 b 2 gnd b 3 b 4 b 5 b 6 v cc b 7 b 8 b 9 gnd b 10 b 11 v cc b 12 b 13 b 14 gnd b 15 b 16 b 17 b 18 b 19 b 20 gnd b 21 b 22 b 23 gnd a 0 a 1 a 2 gnd a 3 a 4 a 5 a 6 v cc a 7 a 8 a 9 gnd a 10 a 11 v cc a 12 a 13 a 14 gnd a 15 a 16 a 17 a 18 a 19 a 20 gnd a 21 a 22 a 23 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 116 115 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 3136 drw 02 117 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 132 131 130 129 128 127 126 125 124 123 122 121 120 119 118 v cc v cc a 24 a 25 a 26 a 27 gnd a 28 a 29 v cc a 30 a 31 a 32 gnd a 33 a 34 a 35 gnd b 35 b 34 b 33 gnd b 32 b 31 b 30 v cc b 29 b 28 b 27 gnd b 26 b 25 b 24 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 ena clka w/ a v cc pga fs 0 odd/ fs 1 nc gnd nc nc nc gnd v cc w/ b clkb enb gnd mba mbb pgb pqfp (pq132-1, order code: pqf) top view
3 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 pin configurations (cont.) tqfp (pn120-1, order code: pf) top view note: 1. nc - no internal connection b 22 b 21 gnd b 20 b 19 b 18 b 17 b 16 b 15 b 14 b 13 b 12 b 11 b 10 gnd b 9 b 8 b 7 v cc b 6 b 5 b 4 b 3 gnd b 2 b 1 b 0 a 23 a 22 a 21 gnd a 20 a 19 a 18 a 17 a 16 a 15 a 14 a 13 a 12 a 11 a 10 gnd a 9 a 8 a 7 v cc a 6 a 5 a 4 a 3 gnd a 2 a 1 a 0 3136 drw 03 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 90 89 88 87 86 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 91 120 119 118 117 116 115 114 113 112 111 110 109 108 107 106 105 104 103 102 101 100 99 98 97 96 95 94 93 92 ena clka w/ a v cc pga mba fs 1 fs 0 odd/ gnd nc nc nc nc mbb pgb v cc w/ b clkb enb 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 b 23 a 24 a 25 a 26 v cc a 27 a 28 a 29 gnd a 30 a 31 a 34 a 35 b 35 gnd b 34 b 33 b 32 b 30 b 31 gnd b 29 b 28 b 27 v cc b 26 b 25 b 24 a 32 a 33
4 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 symbol name i/o description a0-a35 port-a data i/o 36-bit bidirectional data port for side a. aea almost-empty flag o programmable almost-empty flag synchronized to clka. it is low when (port a) the number of words in the fifo2 is less than or equal to the value in the offset register, x. aeb port-b almost-empty o programmable almost-full flag synchronized to clkb. it is low when the flag (portb) number of words in fifo1 is less than or equal to the value in the offset register, x. afa port-a almost-full o programmable almost-full flag synchronized to clka. it is low when the flag (port a) number of empty locations in fifo1 is less than or equal to the value in the offset register, x. afb port-b almost-empty o programmable almost-full flag synchronized to clkb. it is low when the flag (port b) number of empty locations in fifo2 is less than or equal to the value in the offset register, x. b0-b35 port-b data. i/o 36-bit bidirectional data port for side b. clka port-a clock i clka is a continuous clock that synchronizes all data transfers through port- a and can be aynchronous or coincident to clkb. efa , ffa , afa , and aea are synchronized to the low-to-high transition of clka. clkb port-b clock i clkb is a continuous clock that synchronizes all data transfers through port- b and can be asynchronous or coincident to clka. efb , ffb , afb , and aeb are synchronized to the low-to-high transition of clkb. csa port-a chip select i csa must be low to enable a low-to-high transition of clka to read or write data on port-a. the a0-a35 outputs are in the high-impedance state when csa is high. csb port-b chip select i b must be low to enable a low-to-high transition of clkb to read or write data on port-b. the b0-b35 outputs are in the high-impedance state when csb is high. efa port-a empty flag o efa is synchronized to the low-to-high transition of clka. when efa is (port a) low, fifo2 is empty, and reads from its memory are disabled. data can be read from fifo2 to the output register when efa is high. efa is forced low when the device is reset and is set high by the second low-to-high transition of clka after data is loaded into empty fifo2 memory. efb port-b empty flag o efb is synchronized to the low-to-high transition of clkb. when efb is (port b) low, the fifo1 is empty, and reads from its memory are disabled. data can be read from fifo1 to the output register when efb is high. efb is forced low when the device is reset and is set high by the second low- to-high transition of clkb after data is loaded into empty fifo1 memory. ena port-a enable i ena must be high to enable a low-to-high transition of clka to read or write data on port-a. enb port-b enable i enb must be high to enable a low-to-high transition of clkb to read or write data on port-b. ffa port-a full flag o ffa is synchronized to the low-to-high transition of clka. when ffa is (port a) low, fifo1 is full, and writes to its memory are disabled. ffa is forced low when the device is reset and is set high by the second low-to-high transition of clka after reset. ffb port-b full flag o ffb is synchronized to the low-to-high transition of clkb. when ffb is (port b) low, fifo2 is full, and writes to its memory are disabled. ffb is forced low when the device is reset and is set high by the second low-to-high transition of clkb after reset. fs1, fs0 flag-offset selects i the low-to-high transition of rst latches the values of fs0 and fs1, which selects one of four preset values for the almost-full flag and almost- empty flag. mba port-a mailbox select i a high level on mba chooses a mailbox register for a port-a read or write operation. when the a0-a35 outputs are active, a high level on mba selects data from the mail2 register for output, and a low level selects fifo2 output register data for output. pin description
5 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 pin description (continued) symbol name i/o description mbb port-b mailbox i a high level on mbb chooses a mailbox register for a port-b read or write select operation. when the b0-b35 outputs are active, a high level on mbb selects data from the mail1 register for output, and a low level selects fifo1 output register data for output. mbf1 mail1 register flag o mbf1 is set low by a low-to-high transition of clka that writes data to the mail1 register. writes to the mail1 register are inhibited while mbf1 is set low. mbf1 is set high by a low-to-high transition of clkb when a port- b read is selected and mbb is high. mbf1 is set high when the device is reset. mbf2 mail2 register flag o mbf2 is set low by a low-to-high transition of clkb that writes data to the mail2 register. writes to the mail2 register are inhibited while mbf2 is set low. mbf2 is set high by a low-to-high transition of clka when a port- a read is selected and mba is high. mbf2 is set high when the device is reset. odd/ odd/even parity i odd parity is checked on each port when odd/ even is high, and even even select parity is checked when odd/ even is low. odd/ even also selects the type of parity generated for each port if parity generation is enabled for a read operation. pefa port-a parity error o when any byte applied to terminals a0-a35 fails parity, pefa is low. flag (port a) bytes are organized as a0-a8, a9-a17, a18-a26, and a27-a35, with the most significant bit of each byte serving as the parity bit. the type of parity checked is determined by the state of the odd/ even input. the parity trees used to check the a0-a35 inputs are shared by the mail2 register to generate parity if parity generation is selected by pga. therefore, if a mail2 read with parity generation is setup by having w/ r a low, mba high, and pga high, the pefa flag is forcedhigh regardless of the a0-a35 inputs. pefb port-b parity error o when any byte applied to terminals b0-b35 fails parity, pefb is low. flag (port b) bytes are organized as b0-b8, b9-b17, b18-b26, b27-b35 with the most significant bit of each byte serving as the parity bit. the type of parity checked is determined by the state of the odd/ even input. the parity trees used to check the b0-b35 inputs are shared by the mail1 register to generate parity if parity generation is selected by pgb. therefore, if a mail1 read with parity generation is setup by having w/ r b low, mbb high, and pgb high, the pefb flag is forced high regardless of the state of the b0-b35 inputs. pga port-a parity i parity is generated for data reads from port a when pga is high. genera- tion the type of parity generated is selected by the state of the odd/ even input. bytes are organized as a0-a8, a9-a17, a18-a26, and a27-a35. the generated parity bits are output in the most significant bit of each byte. pgb port-b parity i parity is generated for data reads from port b when pgb s high. the type of generation parity generated is selected by the state of the odd/ even input. bytes are organized as b0-b8, b9-b17, b18-b26, and b27-b35. the generated parity bits are output in the most significant bit of each byte. rst reset i to reset the device, four low-to-high transitions of clka and four low-to- high transitions of clkb must occur while rst is low. this sets the afa , afb , mbf1 , and mbf2 flags high and the efa , efb , aea , aeb , ffa, and ffb flags low. the low-to-high transition of rst latches the status of the fs1 and fs0 inouts to select almost-full and almost-empty flag offset. w/ r a port-a write/read i a high selects a write operation and a low selects a read operation on select port a for a low-to-high transition of clka. the a0-a35 outputs are in the high-impedance state when w/ r a is high. w/ r b port-b write/read i a high selects a write operation and a low selects a read operation on select port b for a low-to-high transition of clkb. the b0-b35 outputs are in the high-impedance state when w/ r b is high.
6 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 absolute maximum ratings over operating free-air temperature range (unless otherwise noted) (2) symbol rating commercial unit v cc supply voltage range -0.5 to 7 v v i (2) input voltage range -0.5 to v cc +0.5 v v o (2) output voltage range -0.5 to v cc +0.5 v i ik input clamp current, (v i < 0 or v i > v cc ) 20 ma i ok output clamp current, (v o < 0 or v o > v cc ) 50 ma i out continuous output current, (v o = 0 to v cc ) 50 ma i cc continuous current through v cc or gnd 500 ma t a operating free air temperature range 0 to 70 c t stg storage temperature range -65 to 150 c notes: 1. stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. these are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. exposure to absolute-maximum-rated condi- tions for extended periods may affect device reliability. 2. the input and output voltage ratings may be exceeded provided the input and output current ratings are observed. symbol parameter min. max. unit vcc supply voltage 4.5 5.5 v vih high level input voltage 2 C v vil low-level input voltage C 0.8 v ioh high-level output current C -4 ma iol low-level output current C 8 ma ta operating free-air 0 70 c temperature recommended operating conditions parameter test conditions min. typ. (1) max. unit v oh v cc = 4.5v, i oh = -4 ma 2.4 v v ol v cc = 4.5 v, i ol = 8 ma 0.5 v i li v cc = 5.5 v, v i = v cc or 0 50 m a i lo v cc = 5.5 v, v o = v cc or 0 50 m a i cc v cc 5.5 v, i o = 0 ma, v i = v cc or gnd 1 ma c in v i = 0, f = 1 mhz 4 pf c out v o = 0, f = 1 mhz 8 pf electrical characteristics over recommended operating free-air temperature range (unless otherwise noted) note: 1. all typical values are at v cc = 5 v, t a = 25 c.
7 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 dc electrical characteristics over recommended ranges of supply voltage and operating free-air temperature IDT723612l15 IDT723612l20 IDT723612l30 symbol parameter min. max. min. max. min. max. unit f s clock frequency, clka or clkb C 66.7 C 50 C 33.4 mhz t clk clock cycle time, clka or clkb 15 C 20 C 30 C ns t clkh pulse duration, clka and clkb high 6C8C12Cns t clkl pulse duration, clka and clkb low 6C8C12Cns t ds setup time, a0-a35 before clka - and b0-b35 4C5C6Cns before clkb - t ens1 setup time, csa , w/ r a before clka - ; csb ,6C6C7Cns w/ r b before clkb - t ens2 setup time, ena, before clka - ; enb before 4C5C6Cns clkb - t ens3 setup time, mba before clka - : mbb before 4C5C6Cns clkb - t pgs setup time, odd/ even and pga before 4C5C6Cns clka - ; odd/ even and pgb before clkb - (1) t rsts setup time, rst low before clka - 5C6C7Cns or clkb - (2) t fss setup time, fs0/fs1 before rst high 5C6C7Cns t dh hold time, a0-a35 after clka - and b0-b35 2.5 C 2.5 C 2.5 C ns after clkb - t enh1 hold time, csa w/ r a after clka - ; csb , 2C2C2Cns w/ r b after clkb - t enh2 hold time, ena, after clka - ; enb after clkb - 2.5 C 2.5 C 2.5 C ns t enh3 hold time, mba after clka - ; mbb after clkb - 1C1C1Cns t pgh hold time, odd/ even and pga after clka - ;1C1C1Cns odd/ even and pgb after clkb - (1) t rsth hold time, rst low after clka - or clkb - (2) 5C6C7Cns t fsh hold time, fs0 and fs1 after rst high 4C4C4Cns t skew1 (3) skew time, between clka - and clkb - 8C8C10Cns for efa , efb , ffa , and ffb t skew2 (3) skew time, between clka - and clkb - 9C16C20Cns for aea , aeb , afa , and afb notes: 1. only applies for a clock edge that does a fifo read. 2. requirement to count the clock edge as one of at least four needed to reset a fifo. 3. skew time is not a timimg constraint for proper device operation and is only included to illustrate the timing relation- ship between clka cycle and clkb cycle.
8 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 switching characteristics over recommended ranges of supply voltage and operating free-air temperature, c l = 30pf notes: 1. writing data to the mail1 register when the b0-b35 outputs are active and mbb is high. 2. writing data to the mail2 register when the a0-a35 outputs are active and mba is high. 3. only applies when reading data from a mail register. IDT723612l15 IDT723612l20 IDT723612l30 symbol parameter min. max. min. max. min. max. unit t a access time, clka - to a0-a35 and clkb - 210212215 ns to b0-b35 t wff propagation delay time, clka - to ffa and 210212215 ns clkb - to ffb t ref propagation delay time, clka - to efa and 210212215 ns and clkb - to efb t pae propagation delay time, clka - to aea and 210212215 ns clkb - to aeb t paf propagation delay time, clka - to afa and 210212215 ns clkb - to afb t pmf propagation delay time, clka - to mbf1 low 1 9 1 12 1 15 ns or mbf2 high and clkb - to mbf2 low or mbf1 high t pmr propagation delay time, clka - to b0-b35 (1) 311313315 ns and clkb - to a0-a35 (2) t mdv propagation delay time, mba to a0-a35 valid 1 11 1 11.5 1 12 ns and mbb to b0-b35 valid t pdpe propagation delay time, a0-a35 valid to pefa 310311313 ns valid; b0-b35 valid to pefb valid t pope propagation delay time, odd/ even to pefa 311312314 ns and pefb t popb (3) propagation delay time, odd/ even to parity 2 11 2 12 2 14 ns bits (a8, a17, a26, a35) and (b8, b17, b26, b35) t pepe propagation delay time, w/ r a, csa , ena, mba or 1 11 1 12 1 14 ns pga to pefa ; w/ r b, csb , enb. mbb, pgb to pefb t pepb (3) propagation delay time, w/ r a, csa , ena, mba or 3 12 3 13 3 14 ns pga to parity bits (a8, a17, a26, a35); w/ r b, csb , enb. mbb or pgb to parity bits (b8, b17, b26, b35) t rsf propagation delay time, rst to ( aea , aeb ) 1 15 1 20 1 30 ns low and ( afa , afb , mbf1 , mbf2 ) high t en enable time, csa and w/ r a low to a0-a35 2 10 2 12 2 14 ns active and csb low and w/ r b high to b0-b35 active t dis disable time, csa or w/ r a high to a0-a35 1 819111ns at high impedance and csb high or w/ r b low to b0-b35 at high impedance
9 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 signal descriptions reset the IDT723612 is reset by taking the reset ( rst ) input low for at least four port-a clock (clka) and four port-b clock (clkb) low-to-high transitions. the reset input can switch asynchronously to the clocks. a device reset initializes the internal read and write pointers of each fifo and forces the full flags ( ffa , ffb ) low, the empty flags ( efa , efb ) low, the almost-empty flags ( aea , aeb ) low and the almost-full flags ( afa , afb ) high. a reset also forces the mailbox flags ( mbf1 , mbf2 ) high. after a reset, ffa is set high after two low-to-high transitions of clka and ffb is set high after two low-to-high transitions of clkb. the device must be reset after power up before data is written to its memory. a low-to-high transition on the rst input loads the almost-full and almost-empty registers (x) with the values selected by the flag-select (fs0, fs1) inputs. the values that can be loaded into the registers are shown in table 1. fifo write/read operation the state of port-a data a0-a35 outputs is controlled by the port-a chip select ( csa ) and the port-a write/read select (w/ r a). the a0-a35 outputs are in the high-impedance state when either csa or w/ r a is high. the a0-a35 outputs are active when both csa and w/ r a are low. data is loaded into fifo1 from the a0-a35 inputs on a low-to-high transition of clka when csa is low, w/ r a is high, ena is high, mba is low, and ffa is high. data is read from fifo2 to the a0-a35 outputs by a low-to-high transition of clka when csa is low, w/ r a is low, ena is high, mba is low, and efa is high (see table 2). the port-b control signals are identical to those of port a. the state of the port-b data (b0-b35) outputs is controlled by the port-b chip select ( csb ) and the port-b write/read select (w/ r b). the b0-b35 outputs are in the high-impedance state when either csb or w/ r b is high. the b0-b35 outputs are active when both csb and w/ r b are low. data is loaded into fifo2 from the b0-b35 inputs on a low-to-high transition of clkb when csb is low, w/ r b is high, enb is high, mbb is low, and ffb is high. data is read from fifo1 to the b0-b35 outputs by a low-to-high csb csb w/ r r b enb mbb clkb b0-b35 outputs port functions h x x x x in high-impedance state none l h l x x in high-impedance state none lhhl - in high-impedance state fifo2 write lhhh - in high-impedance state mail2 write l l l l x active, fifo1 output register none llhl - active, fifo1 output register fifo1 read l l l h x active, mail1 register none llhh - active, mail1 register mail1 read (set mbf1 high) table 3. port-b enable function table csa csa w/ r r a ena mba clka a0-a35 outputs port functions h x x x x in high-impedance state none l h l x x in high-impedance state none lhhl - in high-impedance state fifo1 write lhhh - in high-impedance state mail1 write l l l l x active, fifo2 output register none llhl - active, fifo2 output register fifo2 read l l l h x active, mail2 register none llhh - active, mail2 register mail2 read (set mbf2 high) table 2. port-a enable function table almost-full and fs1 fs0 rst rst almost-empty flag offset register (x) hh - 16 hl - 12 lh - 8 ll - 4 table 1. flag programming
10 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 synchronized synchronized number of words to clkb to clka in the fifo1 (1) efb efb aeb aeb afa afa ffa ffa 0llhh 1 to x h l h h (x+1) to [64-(x+1)] h h h h (64-x) to 63 h h l h 64 h h l l synchronized synchronized number of words to clkb to clka in the fifo (1) efa efa aea aea afb afb ffb ffb 0llhh 1 to x h l h h (x+1) to [64-(x+1)] h h h h (64-x) to 63 h h l h 64 h h l l transition of clkb when csb is low, w/ r b is low, enb is high, mbb is low, and efb is high (see table 3). the setup and hold time constraints to the port clocks for the port chip selects ( csa , csb ) and write/read selects (w/ r a, w/ r b) are only for enabling write and read operations and are not related to high-impedance control of the data outputs. if a port enable is low during a clock cycle, the port chip select and write/read select may change states during the setup and hold time window of the cycle. synchronized fifo flags each fifo is synchronized to its port clock through two flip-flop stages. this is done to improve flag reliability by reducing the probability of metastable events on the output when clka and clkb operate asynchronously to one an- other. efa , aea , ffa , and afa are synchronized by clka. efb , aeb , ffb , and afb are synchronized to clkb. tables 4 and 5 show the relationship of each port flag to fifo1 and fifo2. empty flags ( efa efa , efb efb ) the empty flag of a fifo is synchronized to the port clock that reads data from its array. when the empty flag is high, new data can be read to the fifo output register. when the empty flag is low, the fifo is empty and attempted fifo reads are ignored. the read pointer of a fifo is incremented each time a new word is clocked to the output register. the state machine that controls an empty flag monitors a write-pointer and read- pointer comparator that indicates when the fifo sram status is empty, empty+1, or empty+2. a word written to a fifo can be read to the fifo output register in a minimum of three cycles of the empty flag synchronizing clock. therefore, an empty flag is low if a word in memory is the next data to be sent to the fifo output register and two cycles of the port clock that reads data from the fifo have not elapsed since the time the word was written. the empty flag of the fifo is set high by the second low-to-high transition of the synchro- nizing clock, and the new data word can be read to the fifo output register in the following cycle. a low-to-high transition on an empty flag synchroniz- ing clock begins the first synchronization cycle of a write if the clock transition occurs at time t skew1 or greater after the write. otherwise, the subsequent clock cycle can be the first syn- chronization cycle. full flag ( ffa ffa , ffb ffb ) the full flag of a fifo is synchronized to the port clock that writes data to its array. when the full flag is high, a memory location is free in the sram to receive new data. no memory locations are free when the full flag is low and attempted writes to the fifo are ignored. each time a word is written to a fifo, the write pointer is incremented. the state machine that controls a full flag monitors a write-pointer and read pointer comparator that indicates when the fifo sram status is full, full-1, or full-2. from the time a word is read from a fifo, the previous memory location is ready to be written in a minimum of three cycles of the full flag synchronizing clock. therefore, a full flag is low if less than two cycles of the full flag synchronizing clock have elapsed since the next memory write location has been read. the second low-to-high transition on the full flag synchronization clock after the read sets the full flag high and the data can be written in the following clock cycle. a low-to-high transition on a full flag synchronizing clock begins the first synchronization cycle of a read if the clock transition occurs at time t skew1 or greater after the read. otherwise, the subsequent clock cycle can be the first syn- chronization cycle. almost empty flags ( aea aea , aeb aeb ) the almost-empty flag of a fifo is synchronized to the port clock that reads data from its array. the state machine that controls an almost-empty flag monitors a write-pointer comparator that indicates when the fifo sram status is almost empty, almost empty+1, or almost empty+2. the almost-empty state is defined by the value of the almost-full and almost-empty offset register (x). this register is loaded with one of four preset values during a device reset (see reset above). an almost-empty flag is low when the fifo contains table 4. fifo1 flag operation table 5. fifo2 flag operation note: 1. x is the value in the almost-empty flag and almost-full flag offset register.
11 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 x or less words in memory and is high when the fifo contains (x+1) or more words. two low-to-high transitions of the almost-empty flag synchronizing clocks are required after a fifo write for the almost-empty flag to reflect the new level of fill. therefore, the almost-empty flag of a fifo containing (x+1) or more words remains low if two cycles of the synchronizing clock have not elapsed since the write that filled the memory to the (x+1) level. an almost-empty flag is set high by the second low- to-high transition of the synchronizing clock after the fifo write that fills memory to the (x+1) level. a low-to-high transition of an almost-empty flag synchronizing clock begins the first synchronization cycle if it occurs at time t skew2 or greater after the write that fills the fifo to (x+1) words. otherwise, the subsequent synchronizing clock cycle can be the first synchronization cycle (see figure 6 and 7). almost full flags ( afa afa , afb afb ) the almost-full flag of a fifo is synchronized to the port clock that writes data to its array. the state machine that controls an almost-full flag monitors a write-pointer and read- pointer comparator that indicates when the fifo sram status is almost full, almost full-1, or almost full-2. the almost- full state is defined by the value of the almost-full and almost- empty offset register (x). this register is loaded with one of four preset values during a device reset (see reset above). an almost-full flag is low when the fifo contains (64-x) or more words in memory and is high when the fifo contains [64-(x+1)] or less words. two low-to-high transitions of the almost-full flag synchronizing clock are required after a fifo read for the almost-full flag to reflect the new level of fill. therefore, the almost-full flag of a fifo containing [64-(x+1)]or less words remains low if two cycles of the synchronizing clock have not elapsed since the read that reduced the number of words in memory to [64-(x+1)]. an almost-full flag is set high by the second low-to-high transition of the synchronizing clock after the fifo read that reduces the number of words in memory to [64-(x+1)]. a second low-to-high transition of an almost-full flag synchronizing clock begins the first syn- chronization cycle if it occurs at time t skew2 or greater after the read that reduces the number of words in memory to [64- (x+1)]. otherwise, the subsequent synchronizing clock cycle can be the first synchronization cycle (see figure 13 and 14). mailbox registers each fifo has a 36-bit bypass register to pass command and control information between port a and port b without putting it in queue. the mailbox-select (mba, mbb) inputs choose between a mail register and a fifo for a port data transfer operation. a low-to-high transition on clka writes a0-a35 data to the mail1 register when a port-a write is selected by csa , w/ r a, and ena and mba high. a low- to-high transition on clkb writes b0-b35 data to the mail2 register when a port-b write is selected by csb , w/ r b, and enb and mbb is high. writing data to a mail register sets the corresponding flag ( mbf1 or mbf2 ) low. attempted writes to a mail register are ignored while the mail flag is low. when a port's data outputs are active, the data on the bus comes from the fifo output register when the port mailbox- select input (mba, mbb) is low and from the mail register when the port mailbox-select input is high. the mail1 register flag ( mbf1 ) is set high by a low-to-high transition on clkb when a port-b read is selected by csb , w/ r b, and enb and mbb is high. the mail2 register flag ( mbf2 ) is set high by a low-to-high transition on clka when port-a read is selected by csa , w/ r a, and ena and mba is high. the data in a mail register remains intact after it is read and changes only when new data is written to the register. parity checking the port-a inputs (a0-a35) and port-b inputs (b0-b35) each have four parity trees to check the parity of incoming (or outgoing) data. a parity failure on one or more bytes of the input bus is reported by a low level on the port parity error flag ( pefa , pefb ). odd or even parity checking can be selected, and the parity error flags can be ignored if this feature is not desired. parity status is checked on each input bus according to the level of the odd/even parity (odd/even) select input. a parity error on one or more bytes of a port is reported by a low level on the corresponding port parity error flag ( pefa , pefb ) output. port-a bytes are arranged as a0-a8, a9-a17, a18- a26, and a27-a35 with the most significant bit of each byte used as the parity bit. port-b bytes are arranged as b0-b8, b9- b17, b18-b26, and b27-b35, with the most significant bit of each byte used as the parity bit. when odd/even parity is selected, a port parity error flag ( pefa , pefb ) is low if any byte on the port has an odd/even number of low levels applied to the bits. the four parity trees used to check the a0-a35 inputs are shared by the mail2 register when parity generation is se- lected for port-a reads (pga = high). when a port-a read from the mail2 register with parity generation is selected with w/ r a low, csa low, ena high, mba high, and pga high, the port-a parity error flag ( pefa ) is held high regard- less of the levels applied to the a0-a35 inputs. likewise, the parity trees used to check the b0-b35 inputs are shared by the mail1 register when parity generation is selected for port-b reads (pgb = high). when a port-b read from the mail1 register with parity generation is selected with w/ r b low, csb low, enb high, mbb high, and pgb high, the port- b parity error flag ( pefb ) is held high regardless of the levels applied to the b0-b35 inputs. parity generation a high level on the port-a parity generate select (pga) or port-b parity generate select (pgb) enables the IDT723612 to generate parity bits for port reads from a fifo or mailbox register. port-a bytes are arranged as a0-a8, a9-a17, a18- 26, and a27-a35, with the most significant bit of each byte used as the parity bit. port-b bytes are arranged as b0-b8, b9- b17, b18-b26, and b27-b35, with the most significant bit of each byte used as the parity bit. a write to a fifo or mail register stores the levels applied to all thirty-six inputs regard- less of the state of the parity generate select (pga, pgb)
12 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 inputs. when data is read from a port with parity generation selected, the lower eight bits of each byte are used to generate a parity bit according to the level on the odd/ even select. the generated parity bits are substituted for the levels origi- nally written to the most significant bits of each byte as the word is read to the data outputs. parity bits for fifo data are generated after the data is read from sram and before the data is written to the output register. therefore, the port-a parity generate select (pga) and odd/even parity select (odd/ even ) have setup and hold time constraints to the port-a clock (clka) and the port-b parity generate select (pgb) and odd/ even have setup and hold-time constraints to the port-b clock (clkb). these timing constraints only apply for a rising clock edge used to read a new word to the fifo output register. the circuit used to generate parity for the mail1 data is shared by the port-b bus (b0-b35) to check parity and the circuit used to generate parity for the mail2 data is shared by the port-a bus (a0-a35) to check parity. the shared parity trees of a port are used to generate parity bits for the data in a mail register when the port write/read select (w/ r a, w/ r b) input is low, the port mail select (mba, mbb) input is high, chip select ( csa , csb ) is low, enable (ena, enb) is high, and port parity generate select (pga, pgb) is high. gener- ating parity for mail register data does not change the contents of the register.
13 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 figure 1. device reset loading the x register with the value of eight clka rst ffa ffb efb aea clkb efa fs1,fs0 3136 drw 04 t rsts t rsth t fsh t fss t wff t wff t wff 0,1 t ref t ref t pae t paf afa mbf1 , mbf2 aeb afb t rsf t pae t paf t wff
14 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. written to fifo1 figure 2. port-a write cycle timing for fifo1 3136 drw 05 clka ffa ena a0 - a35 mba csa w/ r a t clkh t clkl t clk t ens1 t ens1 t ens3 t ens2 t ds t enh1 t enh1 t enh3 t enh2 t dh w1 (1) w2 (1) t ens2 t enh2 t enh2 t ens2 no operation odd/ even pefa valid valid t pdpe t pdpe high
15 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. written to fifo2 figure 3. port-b write cycle timing for fifo2 3136 drw 06 clkb ffb enb b0 - b35 mbb csb w/ r b t clkh t clkl t clk t ens1 t ens1 t ens3 t ens2 t ds t enh1 t enh1 t enh3 t enh2 t dh w1 (1) w2 (1) t ens2 t enh2 t enh2 t ens2 no operation odd/ even pefb valid valid t pdpe t pdpe high
16 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. read from fifo1 figure 4. port-b read cycle timing for fifo1 figure 5. port-a read cycle timing for fifo2 note: 1. read from fifo2 3136 drw 07 clkb efb enb b0 - b35 mbb csb w/ r b t clk t clkh t clkl t ens2 t a t mdv t en t a t ens2 t enh2 t ens2 t enh2 previous data word 1 word 2 (1) (1) (1) t enh2 no operation pgb, odd/ even high t pgh t pgs t pgh t pgs t dis 3136 drw 08 clka efa ena a0 - a35 mba csa w/ r a t clk t clkh t clkl t ens2 t a t mdv t en t a t ens2 t enh2 t ens2 t enh2 previous data word 1 word 2 (1) (1) (1) t enh2 t dis no operation pga, odd/ even high t pgh t pgs t pgh t pgs
17 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. t skew1 is the minimum time between a rising clka edge and a rising clkb edge for efb to transition high in the next clkb cycle. if the time between the rising clka edge and rising clkb edge is less than t skew1 , then the transition of efb high may occur one clkb cycle later than shown. figure 6. efb efb flag timing and first data read when fifo1 is empty csa w r a mba ffa a0 - a35 clkb efb csb w/ r b mbb ena enb b0 -b35 clka 12 3136 drw 09 t clkh t clkl t clk t ens3 t ens2 t enh3 t enh2 t ds t dh t skew1 t clk t clkl t ens2 t enh2 t a w1 fifo1 empty low high low low low t clkh w1 high (1) t ref t ref
18 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. t skew1 is the minimum time between a rising clkb edge and a rising clka edge for efa to transition high in the next clka cycle. if the time between the rising clkb edge and rising clka edge is less than t skew1 , then the transition of efa high may occur one clka cycle later than shown. figure 7. efa efa flag timing and first data read when fifo2 is empty csb w r b mbb ffb b0 - b35 clka efa csa w/ r a mba enb ena a0 -a35 clkb 12 3136 drw 10 t clkh t clkl t clk t ens3 t ens2 t enh3 t enh2 t ds t dh t skew1 t clk t clkl t ens2 t enh2 t a w1 fifo2 empty low high low low low t clkh w1 high (1) t ref t ref
19 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. t skew1 is the minimum time between a rising clkb edge and a rising clka edge for ffa to transition high in the next clka cycle. if the time between the rising clkb edge and rising clka edge is less than t skew1 , then ffa may transition high one clka cycle later than shown. figure 8. ffa ffa flag timing and first available write when fifo1 is full. csb efb mbb enb b0 - b35 clkb ffa clka csa 3136 drw 11 w r a 12 a0 - a35 mba ena t clk t clkh t clkl t ens2 t enh2 t a t skew1 t clk t clkh t clkl t ens3 t ens2 t ds t enh3 t enh2 t dh to fifo1 previous word in fifo1 output register next word from fifo1 low w/ r b low low high low high (1) fifo1 full t wff t wff
20 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. t skew1 is the minimum time between a rising clka edge and a rising clkb edge for ffb to transition high in the next clkb cycle. if the time between the rising clka edge and rising clkb edge is less than t skew1 , then ffb may transition high one clkb cycle later than shown. figure 9. ffb ffb flag timing and first available write when fifo2 is full csa efa mba ena a0 - a35 clka ffb clkb csb 3136 drw 12 w r b 12 b0 - b35 mbb enb t clk t clkh t clkl t ens2 t enh2 t a t skew1 t clk t clkh t clkl t ens3 t ens2 t ds t enh3 t enh2 t dh to fifo2 previous word in fifo2 output register next word from fifo2 low w/ r a low low high low high (1) fifo2 full t wff t wff
21 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 notes: 1. t skew2 is the minimum time between a rising clkb edge and a rising clka edge for aea to transition high in the next clka cycle. if the time between the rising clkb edge and rising clka edge is less than t skew2 , then aea may transition high one clka cycle later than shown. 2. fifo2 write ( csb = low, w/ r b = high, mbb = low), fifo2 read ( csa = low, w/ r a = low, mba = low). figure 11. timing for aea aea when fifo2 is almost empty notes: 1. t skew2 is the minimum time between a rising clka edge and a rising clkb edge for aeb to transition high in the next clkb cycle. if the time between the rising clka edge and rising clkb edge is less than t skew2 , then aeb may transition high one clkb cycle later than shown. 2. fifo1 write ( csa = low, w/ r a = high, mba = low), fifo1 read ( csb = low, w/ r b = low, mbb = low). figure 10. timing for aeb aeb when fifo1 is almost empty aeb clka enb 3136 drw 13 ena clkb 2 1 t ens2 t enh2 t skew2 t pae t pae t ens2 t enh2 x word in fifo1 (x+1) words in fifo1 (1) aea clkb ena 3136 drw 14 enb clka 2 1 t ens2 t enh2 t skew2 t pae t pae t ens2 t enh2 (x+1) words in fifo2 x words in fifo2 (1)
22 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 notes: 1. t skew2 is the minimum time between a rising clka edge and a rising clkb edge for afa to transition high in the next clka cycle. if the time between the rising clka edge and rising clkb edge is less than t skew2 , then afa may transition high one clkb cycle later than shown. 2. fifo1 write ( csa = low, w/ r a = high, mba = low), fifo1 read ( csb = low, w/ r b = low, mbb = low). figure 12. timing for afa afa when fifo1 is almost full notes: 1. t skew2 is the minimum time between a rising clkb edge and a rising clka edge for afb to transition high in the next clkb cycle. if the time between the rising clkb edge and rising clka edge is less than t skew2 , then afb may transition high one clka cycle later than shown. 2. fifo2 write ( csb = low, w/ r b = high, mbb = low), fifo2 read ( csa = low, w/ r a = low, mba = low). figure 13. timing for afb afb when fifo2 is almost full afa clka enb 3136 drw 15 ena clkb 12 t skew2 t ens2 t enh2 t paf t ens2 t enh2 t paf [64-(x+1)] words in fifo1 (64-x) words in fifo1 (1) afb clkb ena 3136 drw 16 enb clka 12 t skew2 t ens2 t enh2 t paf t ens2 t enh2 t paf [64-(x+1)] words in fifo2 (64-x) words in fifo2 (1)
23 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. port-b parity generation off (pgb = low) figure 14. timing for mail1 register and mbf1 mbf1 flag 3136 drw 17 clka ena a0 - a35 mba csa w/ r a clkb mbf1 csb mbb enb b0 - b35 w/ r b w1 t ens1 t enh1 t ds t dh t pmf t pmf t en t mdv t pmr t ens2 t enh2 t dis w1 (remains valid in mail1 register after read) fifo1 output register
24 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. port-a parity generation off (pga = low) figure 15. timing for mail2 register and mbf2 mbf2 flag 3136 drw 18 clkb enb b0 - b35 mbb csb w/ r b clka mbf2 csa mba ena a0 - a35 w/ r a w1 t ens1 t enh1 t ds t dh t pmf t pmf t ens2 t enh2 t dis t en t mdv t pmr fifo2 output register w1 (remains valid in mail2 register after read)
25 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 figure 16. odd/ even even w/ r r a, mba, and pga to pefa pefa timing note: 1. ena is high, and csa is low figure 17. odd/ even even w/ r r b, mbb, and pgb to pefb pefb timing note: 1. enb is high, and csb is low 3136 drw 19 odd/ even pefa pga mba w/ r a valid valid valid valid t pope t pepe t pope t pepe 3136 drw 20 odd/ even pefb pgb mbb w/ r b valid valid valid valid t pope t pepe t pope t pepe
26 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 figure 18. parity generation timing when reading from mail2 register note: 1. ena is high figure 19. parity generation timing when reading from mail1 register note: 1. enb is high 3136 drw 21 odd/ even a8, a17, a26, a35 pga mba w/ r a mail2 data generated parity generated parity mail2 data csa low t en t pepb t popb t pepb t mdv 3136 drw 22 odd/ even b8, b17, b26, b35 pgb mbb w/ r b mail1 data generated parity generated parity mail1 data csb low t en t pepb t popb t pepb t mdv
27 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 figure 20 calculating power dissipation the i cc(f) current for the graph in figure 20 was taken while simultaneously reading and writing the fifo on the IDT723612 with clka and clkb set to f s . all data inputs and data outputs change state during each clock cycle to consume the highest supply current. data outputs were disconnected to normalize the graph to a zero-capacitance load. once the capacitance load per data-output channel is known, the power dissipation can be calculated with the equation below. with i cc(f ) taken from figure 28, the maximum power dissipation (p d ) of the IDT723612 may be calculated by: p d = v cc x i cc(f) + ? (c l x v cc x (v oh - v ol ) x f o ) where: c l = output capacitance load f o = switching frequency of an output v oh = output high level voltage v ol = output low level voltage when no reads or writes are occurring on the IDT723612, the power dissipated by a single clock (clka or clkb) input running at frequency f s is calculated by: p t = v cc x f s x 0.290 ma/mhz typical characteristics supply current vs clock frequency 010 203040 50 60 80 0 50 100 150 200 250 300 350 400 v cc = 5.0 v ?clock frequency ?mhz f s i cc(f) ?supply current ?ma f data = 1/2 f t a = 25 c c l = 0 pf v cc = 4.5 v v cc = 5.5 v 3136 drw 23 70 s
28 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 note: 1. includes probe and jig capacitance figure 21. load circuit and voltage waveforms 3136 drw 24 parameter measurement information from output under test 30 pf 1.1 k w 5 v 680 w load circuit 3 v gnd timing input data, enable input gnd 3 v 1.5 v 1.5 v voltage waveforms setup and hold times voltage waveforms pulse durations voltage waveforms enable and disable times voltage waveforms propagation delay times 3 v gnd gnd 3 v 1.5 v 1.5 v 1.5 v 1.5 v t w output enable low-level output high-level output 3 v ol gnd 3 v 1.5 v 1.5 v 1.5 v 1.5 v ? oh ov ? gnd oh ol 1.5 v 1.5 v 1.5 v 1.5 v input in-phase output high-level input low-level input v v v v 1.5 v 3 v t s t h t plz t phz t pzl t pzh t pd t pd (1)
29 commercial temperature range IDT723612 bicmos syncbififo ? 64 x 36 x 2 ordering information blank pf pqf 15 20 30 l 723612 3136 drw 25 commercial (0 c to +70 c) thin quad flat pack (tqfp, pn120-1) plastic quad flat pack (pqfp, pq132-1) low power 64 x 36 x 2 syncbififo xxxxxx idt device type xxx x x power speed package process/ temperature range commercial only clock cycle time (t clk ) speed in nanoseconds

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