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| sdr sdram mt48lc64m4a2 C 16 meg x 4 x 4 banks mt48lc32m8a2 C 8 meg x 8 x 4 banks mt48lc16m16a2 C 4 meg x 16 x 4 banks features ? pc100- and pc133-compliant ? fully synchronous; all signals registered on positive edge of system clock ? internal, pipelined operation; column address can be changed every clock cycle ? internal banks for hiding row access/precharge ? programmable burst lengths: 1, 2, 4, 8, or full page ? auto precharge, includes concurrent auto precharge and auto refresh modes ? self refresh mode (not available on at devices) ? auto refresh C 64ms, 8192-cycle refresh (commercial and industrial) C 16ms, 8192-cycle refresh (automotive) ? lvttl-compatible inputs and outputs ? single 3.3v 0.3v power supply options marking ? configurations C 64 meg x 4 (16 meg x 4 x 4 banks) 64m4 C 32 meg x 8 (8 meg x 8 x 4 banks) 32m8 C 16 meg x 16 (4 meg x 16 x 4 banks) 16m16 ? write recovery ( t wr) C t wr = 2 clk a2 ? plastic package C ocpl 1 C 54-pin tsop ii ocpl 1 (400 mil) (standard) tg C 54-pin tsop ii ocpl 1 (400 mil) pb-free p options marking C 60-ball tfbga (x4, x8) (8mm x 16mm) fb C 60-ball tfbga (x4, x8) (8mm x 16mm) pb-free bb C 54-ball vfbga (x16) (8mm x 14 mm) fg 2 C 54-ball vfbga (x16) (8mm x 14 mm) pb-free bg 2 C 54-ball vfbga (x16) (8mm x 8 mm) f4 3 C 54-ball vfbga (x16) (8mm x 8 mm) pb-free b4 3 ? timing C cycle time C 6ns @ cl = 3 (x8, x16 only) -6a C 7.5ns @ cl = 3 (pc133) -75 2 C 7.5ns @ cl = 2 (pc133) -7e ? self refresh C standard none C low power l 2 , 4 ? operating temperature range C commercial (0?c to +70?c) none C industrial (C40?c to +85?c) it C automotive (C40?c to +105?c) at 4 ? revision :d/:g notes: 1. off-center parting line. 2. only available on revision d. 3. only available on revision g. 4. contact micron for availability. table 1: key timing parameters cl = cas (read) latency speed grade clock frequency (mhz) target t rcd- t rp-cl t rcd (ns) t rp (ns) cl (ns) -6a 167 3-3-3 18 18 18 -75 133 3-3-3 20 20 20 -7e 133 2-2-2 15 15 15 256mb: x4, x8, x16 sdram features pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 1 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. products and specifications discussed herein are subject to change by micron without notice.
table 2: address table parameter 64 meg x 4 32 meg x 8 16 meg x 16 configuration 16 meg x 4 x 4 banks 8 meg x 8 x 4 banks 4 meg x 16 x 4 banks refresh count 8k 8k 8k row addressing 8k a[12:0] 8k a[12:0] 8k a[12:0] bank addressing 4 ba[1:0] 4 ba[1:0] 4 ba[1:0] column addressing 2k a[9:0], a11 1k a[9:0] 512 a[8:0] table 3: 256mb sdr part numbering part numbers architecture package mt48lc64m4a2tg 64 meg x 4 54-pin tsop ii mt48lc64m4a2p 64 meg x 4 54-pin tsop ii mt48lc64m4a2fb 1 64 meg x 4 60-ball fbga mt48lc64m4a2bb 1 64 meg x 4 60-ball fbga mt48lc32m8a2tg 32 meg x 8 54-pin tsop ii mt48lc32m8a2p 32 meg x 8 54-pin tsop ii mt48lc32m8a2fb 1 32 meg x 8 60-ball fbga mt48lc32m8a2bb 1 32 meg x 8 60-ball fbga mt48lc16m16a2tg 16 meg x 16 54-pin tsop ii mt48lc16m16a2p 16 meg x 16 54-pin tsop ii mt48lc16m16a2fg 16 meg x 16 54-ball fbga mt48lc16m16a2bg 16 meg x 16 54-ball fbga note: 1. fbga device decoder: www.micron.com/decoder . 256mb: x4, x8, x16 sdram features pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 2 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. contents general description ......................................................................................................................................... 7 automotive temperature .............................................................................................................................. 7 functional block diagrams ............................................................................................................................... 8 pin and ball assignments and descriptions ..................................................................................................... 11 package dimensions ....................................................................................................................................... 15 temperature and thermal impedance ............................................................................................................ 19 electrical specifications .................................................................................................................................. 23 electrical specifications C i dd parameters ........................................................................................................ 25 electrical specifications C ac operating conditions ......................................................................................... 27 functional description ................................................................................................................................... 30 commands .................................................................................................................................................... 31 command inhibit .................................................................................................................................. 31 no operation (nop) ............................................................................................................................... 32 load mode register (lmr) ................................................................................................................... 32 active ...................................................................................................................................................... 32 read ......................................................................................................................................................... 33 write ....................................................................................................................................................... 34 precharge .............................................................................................................................................. 35 burst terminate ................................................................................................................................... 35 refresh ................................................................................................................................................... 36 auto refresh ..................................................................................................................................... 36 self refresh ....................................................................................................................................... 36 truth tables ................................................................................................................................................... 37 initialization .................................................................................................................................................. 42 mode register ................................................................................................................................................ 44 burst length .............................................................................................................................................. 46 burst type .................................................................................................................................................. 46 cas latency ............................................................................................................................................... 48 operating mode ......................................................................................................................................... 48 write burst mode ....................................................................................................................................... 48 bank/row activation ...................................................................................................................................... 49 read operation ............................................................................................................................................. 50 write operation ........................................................................................................................................... 59 burst read/single write .............................................................................................................................. 66 precharge operation .................................................................................................................................. 67 auto precharge ........................................................................................................................................... 67 auto refresh operation ............................................................................................................................. 79 self refresh operation ............................................................................................................................... 81 power-down .................................................................................................................................................. 83 clock suspend ............................................................................................................................................... 84 256mb: x4, x8, x16 sdram features pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 3 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. list of figures figure 1: 64 meg x 4 functional block diagram ................................................................................................. 8 figure 2: 32 meg x 8 functional block diagram ................................................................................................. 9 figure 3: 16 meg x 16 functional block diagram ............................................................................................. 10 figure 4: 54-pin tsop (top view) .................................................................................................................. 11 figure 5: 60-ball fbga (top view) ................................................................................................................. 12 figure 6: 54-ball vfbga (top view) ............................................................................................................... 13 figure 7: 54-pin plastic tsop "tg/p" (400 mil) ............................................................................................... 15 figure 8: 60-ball tfbga "fb/bb" (8mm x 16mm) (x4, x8) ............................................................................... 16 figure 9: 54-ball vfbga "bg/fg" (8mm x 14mm) (x16) .................................................................................. 17 figure 10: 54-ball vfbga "b4/f4" (8mm x 8mm) (x16) ................................................................................... 18 figure 11: example: temperature test point location, 54-pin tsop (top view) ............................................... 21 figure 12: example: temperature test point location, 54-ball vfbga (top view) ............................................ 21 figure 13: example: temperature test point location, 60-ball fbga (top view) .............................................. 22 figure 14: active command ........................................................................................................................ 32 figure 15: read command ........................................................................................................................... 33 figure 16: write command ......................................................................................................................... 34 figure 17: precharge command ................................................................................................................ 35 figure 18: initialize and load mode register .................................................................................................. 43 figure 19: mode register definition ............................................................................................................... 45 figure 20: cas latency .................................................................................................................................. 48 figure 21: example: meeting t rcd (min) when 2 < t rcd (min)/ t ck < 3 .......................................................... 49 figure 22: consecutive read bursts .............................................................................................................. 51 figure 23: random read accesses ................................................................................................................ 52 figure 24: read-to-write ............................................................................................................................ 53 figure 25: read-to-write with extra clock cycle ......................................................................................... 54 figure 26: read-to-precharge .................................................................................................................. 54 figure 27: terminating a read burst ............................................................................................................. 55 figure 28: alternating bank read accesses ..................................................................................................... 56 figure 29: read continuous page burst ......................................................................................................... 57 figure 30: read C dqm operation ................................................................................................................ 58 figure 31: write burst ................................................................................................................................. 59 figure 32: write-to-write .......................................................................................................................... 60 figure 33: random write cycles .................................................................................................................. 61 figure 34: write-to-read ............................................................................................................................ 61 figure 35: write-to-precharge ................................................................................................................. 62 figure 36: terminating a write burst ............................................................................................................ 63 figure 37: alternating bank write accesses ..................................................................................................... 64 figure 38: write C continuous page burst ..................................................................................................... 65 figure 39: write C dqm operation ............................................................................................................... 66 figure 40: read with auto precharge interrupted by a read ......................................................................... 68 figure 41: read with auto precharge interrupted by a write ........................................................................ 69 figure 42: read with auto precharge ............................................................................................................ 70 figure 43: read without auto precharge ....................................................................................................... 71 figure 44: single read with auto precharge .................................................................................................. 72 figure 45: single read without auto precharge ............................................................................................. 73 figure 46: write with auto precharge interrupted by a read ........................................................................ 74 figure 47: write with auto precharge interrupted by a write ...................................................................... 74 figure 48: write with auto precharge ........................................................................................................... 75 figure 49: write without auto precharge ..................................................................................................... 76 figure 50: single write with auto precharge ................................................................................................. 77 256mb: x4, x8, x16 sdram features pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 4 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 51: single write without auto precharge ............................................................................................ 78 figure 52: auto refresh mode ........................................................................................................................ 80 figure 53: self refresh mode .......................................................................................................................... 82 figure 54: power-down mode ........................................................................................................................ 83 figure 55: clock suspend during write burst ............................................................................................... 84 figure 56: clock suspend during read burst ................................................................................................. 85 figure 57: clock suspend mode ..................................................................................................................... 86 256mb: x4, x8, x16 sdram features pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 5 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. list of tables table 1: key timing parameters ....................................................................................................................... 1 table 2: address table ..................................................................................................................................... 2 table 3: 256mb sdr part numbering ............................................................................................................... 2 table 4: pin and ball descriptions .................................................................................................................. 14 table 5: temperature limits .......................................................................................................................... 19 table 6: thermal impedance simulated values ............................................................................................... 20 table 7: absolute maximum ratings .............................................................................................................. 23 table 8: dc electrical characteristics and operating conditions ..................................................................... 23 table 9: capacitance ..................................................................................................................................... 24 table 10: i dd specifications and conditions (x4, x8, x16) revision d ................................................................ 25 table 11: i dd specifications and conditions (x4, x8, x16) revision g ................................................................ 25 table 12: electrical characteristics and recommended ac operating conditions ............................................ 27 table 13: ac functional characteristics ......................................................................................................... 28 table 14: truth table C commands and dqm operation ................................................................................. 31 table 15: truth table C current state bank n , command to bank n .................................................................. 37 table 16: truth table C current state bank n, command to bank m ................................................................. 39 table 17: truth table C cke ........................................................................................................................... 41 table 18: burst definition table ..................................................................................................................... 47 256mb: x4, x8, x16 sdram features pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 6 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. general description the 256mb sdram is a high-speed cmos, dynamic random-access memory contain- ing 268,435,456 bits. it is internally configured as a quad-bank dram with a synchro- nous interface (all signals are registered on the positive edge of the clock signal, clk). each of the x4s 67,108,864-bit banks is organized as 8192 rows by 2048 columns by 4 bits. each of the x8s 67,108,864-bit banks is organized as 8192 rows by 1024 columns by 8 bits. each of the x16s 67,108,864-bit banks is organized as 8192 rows by 512 columns by 16 bits. read and write accesses to the sdram are burst-oriented; accesses start at a selected location and continue for a programmed number of locations in a programmed se- quence. accesses begin with the registration of an active command, which is then fol- lowed by a read or write command. the address bits registered coincident with the active command are used to select the bank and row to be accessed (ba[1:0] select the bank; a[12:0] select the row). the address bits registered coincident with the read or write command are used to select the starting column location for the burst access. the sdram provides for programmable read or write burst lengths (bl) of 1, 2, 4, or 8 locations, or the full page, with a burst terminate option. an auto precharge function may be enabled to provide a self-timed row precharge that is initiated at the end of the burst sequence. the 256mb sdram uses an internal pipelined architecture to achieve high-speed oper- ation. this architecture is compatible with the 2 n rule of prefetch architectures, but it also allows the column address to be changed on every clock cycle to achieve a high- speed, fully random access. precharging one bank while accessing one of the other three banks will hide the precharge cycles and provide seamless, high-speed, ran- dom-access operation. the 256mb sdram is designed to operate in 3.3v memory systems. an auto refresh mode is provided, along with a power-saving, power-down mode. all inputs and out- puts are lvttl-compatible. sdrams offer substantial advances in dram operating performance, including the ability to synchronously burst data at a high data rate with automatic column-address generation, the ability to interleave between internal banks to hide precharge time, and the capability to randomly change column addresses on each clock cycle during a burst access. automotive temperature the automotive temperature (at) option adheres to the following specifications: ? 16ms refresh rate ? self refresh not supported ? ambient and case temperature cannot be less than C40c or greater than +105c 256mb: x4, x8, x16 sdram general description pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 7 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. functional block diagrams figure 1: 64 meg x 4 functional block diagram 13 ras# cas# row- address mux clk cs# we# cke control logic column- address counter/ latch mode register 11 command decode a[12:0] ba[1:0] dqm 13 address register 15 2048 (x4) 8192 i/o gating dqm mask logic read data latch write drivers column decoder bank0 memory array (8192 x 2048 x 4) bank0 row- address latch & decoder 8192 sense amplifiers bank control logic dq[3:0] 4 4 data input register data output register 4 12 bank1 bank2 bank3 13 11 2 1 1 2 refresh counter 256mb: x4, x8, x16 sdram functional block diagrams pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 8 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 2: 32 meg x 8 functional block diagram 13 ras# cas# row- address mux clk cs# we# cke control logic column- address counter/ latch mode register 10 command decode a[12:0] ba[1:0] dqm 13 address register 15 1024 (x8) 8192 i/o gating dqm mask logic read data latch write drivers column decoder bank0 memory array (8192 x 1024 x 8) bank0 row- address latch & decoder 8192 sense amplifiers bank control logic dq[7:0] 8 8 data input register data output register 8 12 bank1 bank2 bank3 13 10 2 1 1 2 refresh counter 256mb: x4, x8, x16 sdram functional block diagrams pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 9 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 3: 16 meg x 16 functional block diagram 13 ras# cas# row- address mux clk cs# we# cke control logic column- address counter/ latch mode register 9 command decode a[12:0] ba[1:0] dqml, dqmh 13 address register 15 512 (x16) 8192 i/o gating dqm mask logic read data latch write drivers column decoder bank0 memory array (8192 x 512 x 16) bank0 row- address latch & decoder 8192 sense amplifiers bank control logic dq[15:0] 16 16 data input register data output register 16 12 bank1 bank2 bank3 13 9 2 2 2 2 refresh counter 256mb: x4, x8, x16 sdram functional block diagrams pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 10 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. pin and ball assignments and descriptions figure 4: 54-pin tsop (top view) v dd dq0 v ddq dq1 dq2 v ssq dq3 dq4 v ddq dq5 dq6 v ssq dq7 v dd dqml we# cas# ras# cs# ba0 ba1 a10 a0 a1 a2 a3 v dd 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 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 v ss dq15 v ssq dq14 dq13 v ddq dq12 dq11 v ssq dq10 dq9 v ddq dq8 v ss nc dqmh clk cke a12 a11 a9 a8 a7 a6 a5 a4 v ss x8 x16 x16 x8 x4 x4 - dq0 - nc dq1 - nc dq2 - nc dq3 - nc - nc - - - - - - - - - - - - - nc - nc dq0 - nc nc - nc dq1 - nc - nc - - - - - - - - - - - - - dq7 - nc dq6 - nc dq5 - nc dq4 - nc - - dqm - - - - - - - - - - - - nc - nc dq3 - nc nc - nc dq2 - nc - - dqm - - - - - - - - - - - notes: 1. the # symbol indicates that the signal is active low. a dash (-) indicates that the x8 and x4 pin function is the same as the x16 pin function. 2. package may or may not be assembled with a location notch. 256mb: x4, x8, x16 sdram pin and ball assignments and descriptions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 11 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 5: 60-ball fbga (top view) a b c d e f g h j k l m n p r 1 2 3 4 5 6 7 8 depopulated balls nc v ss nc v ssq v ddq dq3 nc nc nc v ssq v ddq dq2 nc nc nc v ss nc dqm nc ck a12 cke a11 a9 a8 a7 a6 a5 a4 v ss v dd nc v ddq nc dq0 v ssq nc nc v ddq nc dq1 v ssq nc nc v dd nc we# cas# ras# nc nc cs# ba1 ba0 a0 a10 a2 a1 v dd a3 a b c d e f g h j k l m n p r 1 2 3 4 5 6 7 8 depopulated balls dq7 v ss nc v ssq v ddq dq6 dq5 nc nc v ssq v ddq dq4 nc nc nc v ss nc dqm nc ck a12 cke a11 a9 a8 a7 a6 a5 a4 v ss v dd dq0 v ddq nc dq1 v ssq nc dq2 v ddq nc dq3 v ssq nc nc v dd nc we# cas# ras# nc nc cs# ba1 ba0 a0 a10 a2 a1 v dd a3 64 meg x 4 sdram 8mm x 16mm fb 32 meg x 8 sdram 8mm x 16mm fb 256mb: x4, x8, x16 sdram pin and ball assignments and descriptions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 12 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 6: 54-ball vfbga (top view) a b c d e f g h j 1 2 3 4 5 6 7 8 9 depopulated balls v ss dq15 dq14 dq13 dq12 dq11 dq10 dq9 dq8 nc udqm clk a12 a11 a8 a7 v ss a5 v ssq v ddq v ssq v ddq v ss cke a9 a6 a4 v ddq v ssq v ddq v ssq v dd cas# ba0 a0 a3 dq0 v dd dq2 dq1 dq4 dq3 dq6 dq5 ldqm dq7 ras# we# ba1 cs# a1 a10 a2 v dd note: 1. the balls at a4, a5, and a6 are absent from the physical package. they are included to illustrate that rows 4, 5, and 6 exist, but contain no solder balls. 256mb: x4, x8, x16 sdram pin and ball assignments and descriptions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 13 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. table 4: pin and ball descriptions symbol type description clk input clock: clk is driven by the system clock. all sdram input signals are sampled on the positive edge of clk. clk also increments the internal burst counter and controls the output registers. cke input clock enable: cke activates (high) and deactivates (low) the clk signal. deactivating the clock provides precharge power-down and self refresh operation (all banks idle), active power-down (row active in any bank), or clock suspend operation (burst/access in pro- gress). cke is synchronous except after the device enters power-down and self refresh modes, where cke becomes asynchronous until after exiting the same mode. the input buffers, in- cluding clk, are disabled during power-down and self refresh modes, providing low standby power. cke may be tied high. cs# input chip select: cs# enables (registered low) and disables (registered high) the command decod- er. all commands are masked when cs# is registered high, but read/write bursts already in progress will continue, and dqm operation will retain its dq mask capability while cs# is high. cs# provides for external bank selection on systems with multiple banks. cs# is consid- ered part of the command code. cas#, ras#, we# input command inputs: ras#, cas#, and we# (along with cs#) define the command being entered. x4, x8: dqm x16: dqml, dqmh ldqm, udqm (54-ball) input input/output mask: dqm is sampled high and is an input mask signal for write accesses and an output enable signal for read accesses. input data is masked during a write cycle. the output buffers are high-z (two-clock latency) during a read cycle. ldqm corresponds to dq[7:0], and udqm corresponds to dq[15:8]. ldqm and udqm are considered same-state when referenced as dqm. ba[1:0] input bank address input(s): ba[1:0] define to which bank the active, read, write, or precharge command is being applied. a[12:0] input address inputs: a[12:0] are sampled during the active command (row address a[12:0]) and read or write command (column address a[9:0] and a11 for x4; a[9:0] for x8; a[8:0] for x16; with a10 defining auto precharge) to select one location out of the memory array in the re- spective bank. a10 is sampled during a precharge command to determine if all banks are to be precharged (a10 high) or bank selected by ba[1:0] (low). the address inputs also provide the op-code during a load mode register command. x16: dq[15:0] i/o data input/output: data bus for x16 (pins 4, 7, 10, 13, 42, 45, 48, and 51 are nc for x8; and pins 2, 4, 7, 8, 10, 13, 42, 45, 47, 48, 51, and 53 are nc for x4). x8: dq[7:0] i/o data input/output: data bus for x8 (pins 2, 8, 47, 53 are nc for x4). x4: dq[3:0] i/o data input/output: data bus for x4. v ddq supply dq power: dq power to the die for improved noise immunity. v ssq supply dq ground: dq ground to the die for improved noise immunity. v dd supply power supply: +3.3v 0.3v. v ss supply ground. nc C these should be left unconnected. for x4 and x8 parts, g1 is a no connect, but may be used as a12 in future designs. 256mb: x4, x8, x16 sdram pin and ball assignments and descriptions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 14 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. package dimensions figure 7: 54-pin plastic tsop "tg/p" (400 mil) see detail a 0.10 +0.10 -0.05 0.15 +0.03 -0.02 2x r 1.00 2x r 0.75 0.80 typ (for reference only) 0.71 0.50 0.10 pin #1 id detail a 22.22 0.08 10.16 0.08 11.76 0.20 0.375 0.075 typ 1.2 max 0.25 0.80 gage plane plated lead finish: 90% sn, 10% pb or 100%sn package may or may not be assembled with a location notch. 2x 2.28 package may or may not be assembled with a location notch. plastic package material: epoxy novolac package width and length do not include mold protrusion. allowable protrusion is 0.25 per side. 0.10 22.42 notes: 1. all dimensions are in millimeters. 2. package width and length do not include mold protrusion; allowable mold protrusion is 0.25mm per side. 3. 2x means the notch is present in two locations (both ends of the device). 4. package may or may not be assembled with a location notch. 256mb: x4, x8, x16 sdram package dimensions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 15 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 8: 60-ball tfbga "fb/bb" (8mm x 16mm) (x4, x8) ball a1 id 1.1 0.1 8 0.1 ball a1 id 60x ?0.45 dimensions apply to solder balls post-reflow on ?0.33 nsmd ball pads. 0.8 typ 11.2 ctr 16 0.1 0.12 a a seating plane 6.4 ctr 0.8 typ 0.25 min 8 7 2 1 a b c d e f g h j k l m n p r notes: 1. all dimensions are in millimeters. 2. recommended pad size for pcb is 0.33mm 0.025mm. 3. topside part-marking decoder is available at www.micron.com/decoder . 256mb: x4, x8, x16 sdram package dimensions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 16 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 9: 54-ball vfbga "bg/fg" (8mm x 14mm) (x16) ball a1 id 1.00 max mold compound: epoxy novolac substrate material: plastic laminate solder ball material: 62% sn, 36% pb, 2% ag or 96.5% sn, 3%ag, 0.5% cu solder mask defined ball pads: ? 0.40 14.00 0.10 ball a1 ball a9 ball a1 id 0.80 typ 0.80 typ 7.00 0.05 8.00 0.10 4.00 0.05 3.20 0.05 3.20 0.05 0.65 0.05 seating plane c 6.40 6.40 0.12 c 54x ?0.45 solder ball diameter refers to post reflow condition. the pre- reflow diameter is ?0.42 c l c l notes: 1. all dimensions are in millimeters. 2. recommended pad size for pcb is 0.4mm 0.065mm. 3. topside part-marking decoder is available at www.micron.com/decoder . 256mb: x4, x8, x16 sdram package dimensions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 17 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 10: 54-ball vfbga "b4/f4" (8mm x 8mm) (x16) seating plane 0.12 a ball a1 id a 6.4 ctr 8 0.1 0.8 typ 6.4 ctr 8 0.1 0.8 typ ball a1 id (covered by sr) a b c d e f g h j 1 2 3 7 8 9 0.9 0.1 0.25 min 54x ?0.45 dimensions apply to solder balls post- reflow on ? ?0.40 smd ball pads. notes: 1. all dimensions are in millimeters. 2. recommended pad size for pcb is 0.4mm 0.065mm. 3. solder ball material: sac305 (96.5% sn, 3% ag, 0.5% cu) or sac105 (98.5% sn, 1% ag, 0.5% cu). 4. topside part-marking decoder is available at www.micron.com/decoder . 256mb: x4, x8, x16 sdram package dimensions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 18 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. temperature and thermal impedance it is imperative that the sdram devices temperature specifications, shown in table 5 (page 19), be maintained to ensure the junction temperature is in the proper operat- ing range to meet data sheet specifications. an important step in maintaining the prop- er junction temperature is using the devices thermal impedances correctly. the ther- mal impedances are listed in table 6 (page 20) for the applicable die revision and packages being made available. these thermal impedance values vary according to the density, package, and particular design used for each device. incorrectly using thermal impedances can produce significant errors. read micron technical note tn-00-08, thermal applications prior to using the thermal impedan- ces listed in table 6 (page 20). to ensure the compatibility of current and future de- signs, contact micron applications engineering to confirm thermal impedance values. the sdram devices safe junction temperature range can be maintained when the t c specification is not exceeded. in applications where the devices ambient temperature is too high, use of forced air and/or heat sinks may be required to satisfy the case tem- perature specifications. table 5: temperature limits parameter symbol min max unit notes operating case temperature commercial t c 0 80 c 1, 2, 3, 4 industrial C40 90 automotive C40 105 junction temperature commercial t j 0 85 c 3 industrial C40 95 automotive C40 110 ambient temperature commercial t a 0 70 c 3, 5 industrial C40 85 automotive C40 105 peak reflow temperature t peak C 260 c notes: 1. max operating case temperature, t c , is measured in the center of the package on the top side of the device, as shown in figure 11 (page 21), figure 12 (page 21), and fig- ure 13 (page 22). 2. device functionality is not guaranteed if the device exceeds maximum t c during opera- tion. 3. all temperature specifications must be satisfied. 4. the case temperature should be measured by gluing a thermocouple to the top-center of the component. this should be done with a 1mm bead of conductive epoxy, as de- fined by the jedec eia/jesd51 standards. take care to ensure that the thermocouple bead is touching the case. 5. operating ambient temperature surrounding the package. 256mb: x4, x8, x16 sdram temperature and thermal impedance pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 19 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. table 6: thermal impedance simulated values die revision package substrate ja (c/w) airflow = 0m/s ja (c/w) airflow = 1m/s ja (c/w) airflow = 2m/s jb (c/w) jc (c/w) d 54-pin tsop (tg, p) low con- ductivity 81 63.8 57.6 45.3 10.3 high con- ductivity 55 47.3 44.5 39.1 54-ball vfbga (bg, fg) low con- ductivity 64.9 50.8 44.8 31.4 3.2 high con- ductivity 51.5 41.6 38.1 31.4 60-ball fbga (bb, fb) low con- ductivity 67 51.2 47.8 19.7 6.7 high con- ductivity 40.9 35.1 32.2 18.6 g 54-pin tsop (tg, p) low con- ductivity 122.3 105.6 98.1 89.5 20.7 high con- ductivity 101.9 93.5 88.8 87.6 54-ball vfbga (b4, f4) low con- ductivity 96.9 81.9 81.9 69.5 11.5 high con- ductivity 74.0 66.3 62.7 60.7 60-ball fbga (bb, fb) low con- ductivity 68.8 55.9 51.1 42.1 10.9 high con- ductivity 47.9 42.0 39.9 34.9 notes: 1. for designs expected to last beyond the die revision listed, contact micron applications engineering to confirm thermal impedance values. 2. thermal resistance data is sampled from multiple lots, and the values should be viewed as typical. 3. these are estimates; actual results may vary. 256mb: x4, x8, x16 sdram temperature and thermal impedance pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 20 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 11: example: temperature test point location, 54-pin tsop (top view) 22.22mm 11.11mm test point 10.16mm 5.08mm note: 1. package may or may not be assembled with a location notch. figure 12: example: temperature test point location, 54-ball vfbga (top view) 8.00mm 4.00mm test point 14.00mm 7.00mm 256mb: x4, x8, x16 sdram temperature and thermal impedance pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 21 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 13: example: temperature test point location, 60-ball fbga (top view) 8.00mm 4.00mm test point 8.00mm 16.00mm 256mb: x4, x8, x16 sdram temperature and thermal impedance pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 22 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. electrical specifications stresses greater than those listed may cause permanent damage to the device. this is a stress rating only, and functional operation of the device at these or any other condi- tions above those indicated in the operational sections of this specification is not im- plied. exposure to absolute maximum rating conditions for extended periods may affect reliability. table 7: absolute maximum ratings voltage/temperature symbol min max unit notes voltage on v dd /v ddq supply relative to v ss v dd /v ddq C1 4.6 v 1 voltage on inputs, nc, or i/o balls relative to v ss v in C1 4.6 storage temperature (plastic) t stg C55 150 c power dissipation C C 1 w note: 1. v dd and v ddq must be within 300mv of each other at all times. v ddq must not exceed v dd . table 8: dc electrical characteristics and operating conditions notes 1C3 apply to all parameters and conditions; v dd /v ddq = 3.3v 0.3v parameter/condition symbol min max unit notes supply voltage v dd , v ddq 3 3.6 v input high voltage: logic 1; all inputs v ih 2 v dd + 0.3 v 4 input low voltage: logic 0; all inputs v il C0.3 0.8 v 4 output high voltage: i out = C4ma v oh 2.4 C v output low voltage: i out = 4ma v ol C 0.4 v input leakage current: any input 0v v in v dd (all other balls not under test = 0v) i l C5 5 a output leakage current: dq are disabled; 0v v out v ddq i oz C5 C5 a operating temperature: commercial t a 0 70 ?c industrial t a C40 85 ?c automotive t a C40 105 ?c notes: 1. all voltages referenced to v ss . 2. the minimum specifications are used only to indicate cycle time at which proper opera- tion over the full temperature range is ensured; (0c t a +70c (commercial), C40c t a +85c (industrial), and C40c t a +105c (automotive)). 3. an initial pause of 100 s is required after power-up, followed by two auto refresh commands, before proper device operation is ensured. (v dd and v ddq must be powered up simultaneously. v ss and v ssq must be at same potential.) the two auto refresh command wake-ups should be repeated any time the t ref refresh requirement is excee- ded. 4. v ih overshoot: v ih,max = v ddq + 2v for a pulse width 3ns, and the pulse width cannot be greater than one-third of the cycle rate. v il undershoot: v il,min = C2v for a pulse width 3ns. 256mb: x4, x8, x16 sdram electrical specifications pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 23 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. table 9: capacitance note 1 applies to all parameters and conditions package parameter symbol min max unit notes tsop package input capacitance: clk c l1 2.5 3.5 pf 2 input capacitance: all other input-only balls c l2 2.5 3.8 pf 3 input/output capacitance: dq c l0 4 6 pf 4 fbga package input capacitance: clk c l1 1.5 3.5 pf 5 input capacitance: all other input-only balls c l2 1.5 3.8 pf 6 input/output capacitance: dq c l0 3 6 pf 7 notes: 1. this parameter is sampled. v dd , v ddq = 3.3v; f = 1 mhz, t a = 25c; pin under test biased at 1.4v. 2. pc100 specifies a maximum of 4pf. 3. pc100 specifies a maximum of 5pf. 4. pc100 specifies a maximum of 6.5pf. 5. pc133 specifies a minimum of 2.5pf. 6. pc133 specifies a minimum of 2.5pf. 7. pc133 specifies a minimum of 3.0pf. 256mb: x4, x8, x16 sdram electrical specifications pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 24 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. electrical specifications C i dd parameters table 10: i dd specifications and conditions (x4, x8, x16) revision d notes 1C5 apply to all parameters and conditions; v dd /v ddq = +3.3v 0.3v parameter/condition symbol max unit notes -6a -7e -75 operating current: active mode; burst = 2; read or write; t rc = t rc (min) i dd1 135 135 125 ma 6, 7, 8, 9 standby current: power-down mode; all banks idle; cke = low i dd2 2 2 2 ma 9 standby current: active mode; cke = high; cs# = high; all banks active after t rcd met; no accesses in progress i dd3 40 40 40 ma 6, 8, 9, 10 operating current: burst mode; page burst; read or write; all banks active i dd4 135 135 135 ma 6, 7, 8, 9 auto refresh current: cke = high; cs# = high t rfc = t rfc (min) i dd5 285 285 270 ma 6, 7, 8, 9, 10, 11 t rfc = 7.813 s i dd6 3.5 3.5 3.5 ma t rfc = 1.953 s (at) i dd6 8 8 8 ma self refresh current: cke 0.2v standard i dd7 2.5 2.5 2.5 ma low power (l) i dd7 C 1.5 1.5 ma 12 table 11: i dd specifications and conditions (x4, x8, x16) revision g notes 1C5 apply to all parameters and conditions; v dd /v ddq = +3.3v 0.3v parameter/condition symbol max unit notes -6a -7e operating current: active mode; burst = 2; read or write; t rc = t rc (min) i dd1 100 100 ma 6, 7, 8, 9 standby current: power-down mode; all banks idle; cke = low i dd2 2.5 2.5 ma 9 standby current: active mode; cke = high; cs# = high; all banks ac- tive after t rcd met; no accesses in progress i dd3 35 35 ma 6, 8, 9, 10 operating current: burst mode; page burst; read or write; all banks active i dd4 100 100 ma 6, 7, 8, 9 auto refresh current: cke = high; cs# = high t rfc = t rfc (min) i dd5 150 150 ma 6, 7, 8, 9, 10, 11 t rfc = 7.813 s i dd6 4 4 ma t rfc = 1.953 s (at) i dd6 8 8 ma self refresh current: cke 0.2v standard i dd7 3 3 ma low power (l) i dd7 1.5 1.5 ma 12 notes: 1. all voltages referenced to v ss . 2. the minimum specifications are used only to indicate cycle time at which proper opera- tion over the full temperature range is ensured; (0c t a +70c (commercial), C40c t a +85c (industrial), and C40c t a +105c (automotive)). 3. an initial pause of 100 s is required after power-up, followed by two auto refresh commands, before proper device operation is ensured. (v dd and v ddq must be powered up simultaneously. v ss and v ssq must be at same potential.) the two auto refresh 256mb: x4, x8, x16 sdram electrical specifications C i dd parameters pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 25 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. command wake-ups should be repeated any time the t ref refresh requirement is excee- ded. 4. ac operating and i dd test conditions have v il = 0v and v ih = 3.0v using a measurement reference level of 1.5v. if the input transition time is longer than 1ns, then the timing is measured from v il, max and v ih,min and no longer from the 1.5v midpoint. clk should always be 1.5v referenced to crossover. refer to micron technical note tn-48-09. 5. i dd specifications are tested after the device is properly initialized. 6. i dd is dependent on output loading and cycle rates. specified values are obtained with minimum cycle time and the outputs open. 7. the i dd current will increase or decrease proportionally according to the amount of fre- quency alteration for the test condition. 8. address transitions average one transition every two clocks. 9. for -75, cl = 3 and t ck = 7.5ns; for -7e, cl = 2 and t ck = 7.5ns. 10. other input signals are allowed to transition no more than once every two clocks and are otherwise at valid v ih or v il levels. 11. cke is high during refresh command period t rfc (min) else cke is low. the i dd6 limit is actually a nominal value and does not result in a fail value. 12. enables on-chip refresh and address counters. 13. pc100 specifies a maximum of 4pf. 14. pc100 specifies a maximum of 5pf. 256mb: x4, x8, x16 sdram electrical specifications C i dd parameters pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 26 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. electrical specifications C ac operating conditions table 12: electrical characteristics and recommended ac operating conditions notes 1C5 apply to all parameters and conditions parameter symbol -6a -7e -75 unit notes min max min max min max access time from clk (positive edge) cl = 3 t ac(3) C 5.4 C 5.4 C 5.4 ns 7 cl = 2 t ac(2) C 7.5 6 C 5.4 C 6 ns 7 cl = 1 t ac(1) C 17 6 C C C C ns 7 address hold time t ah 0.8 C 0.8 C 0.8 C ns address setup time t as 1.5 C 1.5 C 1.5 C ns clk high-level width t ch 2.5 C 2.5 C 2.5 C ns clk low-level width t cl 2.5 C 2.5 C 2.5 C ns clock cycle time cl = 3 t ck(3) 6 C 7 C 7.5 C ns 8 cl = 2 t ck(2) 10 6 C 7.5 C 10 C ns 8 cl = 1 t ck(1) 20 6 C C C C C ns 8 cke hold time t ckh 0.8 C 0.8 C 0.8 C ns cke setup time t cks 1.5 C 1.5 C 1.5 C ns cs#, ras#, cas#, we#, dqm hold time t cmh 0.8 C 0.8 C 0.8 C ns cs#, ras#, cas#, we#, dqm setup time t cms 1.5 C 1.5 C 1.5 C ns data-in hold time t dh 0.8 C 0.8 C 0.8 C ns data-in setup time t ds 1.5 C 1.5 C 1.5 C ns data-out high-z time cl = 3 t hz(3) C 5.4 C 5.4 C 5.4 ns 9 cl = 2 t hz(2) C 7.5 6 C 5.4 C 6 ns 9 cl = 1 t hz(1) C 17 6 C C C C ns 9 data-out low-z time t lz 1 C 1 C 1 C ns data-out hold time (load) t oh 3 C 3 C 3 C ns data-out hold time (no load) t oh n 1.8 C 1.8 C 1.8 C ns 10 active-to-precharge command t ras 42 120,000 37 120,000 44 120,000 ns active-to-active command period t rc 60 C 60 C 66 C ns 11 active-to-read or write delay t rcd 18 C 15 C 20 C ns refresh period (8192 rows) t ref C 64 C 64 C 64 ms refresh period C automotive (8192 rows) t ref at C 16 C 16 C 16 ms auto refresh period t rfc 60 C 66 C 66 C ns precharge command period t rp 18 C 15 C 20 C ns active bank a to active bank b com- mand t rrd 12 C 14 C 15 C ns transition time t t 0.3 1.2 0.3 1.2 0.3 1.2 ns 12 write recovery time t wr 1 clk + 6ns C 1 clk + 7ns C 1 clk + 7.5ns C ns 13 12 C 14 C 15 C ns 14 256mb: x4, x8, x16 sdram electrical specifications C ac operating conditions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 27 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. table 12: electrical characteristics and recommended ac operating conditions (continued) notes 1C5 apply to all parameters and conditions parameter symbol -6a -7e -75 unit notes min max min max min max exit self refresh-to-active command t xsr 67 C 67 C 75 C ns 15 table 13: ac functional characteristics notes 2C5 apply to all parameters and conditions parameter symbol -6a -7e -75 unit notes last data-in to burst stop command t bdl 1 1 1 t ck 16 read/write command to read/write command t ccd 1 1 1 t ck 16 last data-in to new read/write command t cdl 1 1 1 t ck 16 cke to clock disable or power-down entry mode t cked 1 1 t ck 17 data-in to active command t dal 5 4 5 t ck 18, 19 data-in to precharge command t dpl 2 2 2 t ck 19, 20 dqm to input data delay t dqd 0 0 0 t ck 16 dqm to data mask during writes t dqm 0 0 0 t ck 16 dqm to data high-z during reads t dqz 2 2 2 t ck 16 write command to input data delay t dwd 0 0 0 t ck 16 load mode register command to active or refresh command t mrd 2 2 2 t ck 21 cke to clock enable or power-down exit setup mode t ped 1 1 1 t ck 17 last data-in to precharge command t rdl 2 2 2 t ck 19, 20 data-out high-z from precharge command cl = 3 t roh(3) 3 3 3 t ck 16 cl = 2 t roh(2) 2 2 2 t ck 16 cl = 1 t roh(1) 1 C C t ck 16 notes: 1. minimum specifications are used only to indicate the cycle time at which proper opera- tion over the full temperature range is ensured: 0?c t a +70?c (commercial) -40?c t a +85?c (industrial) -40?c t a +105?c (automotive) 2. an initial pause of 100 s is required after power-up, followed by two auto refresh commands, before proper device operation is ensured. (v dd and v ddq must be powered up simultaneously. v ss and v ssq must be at same potential.) the two auto refresh command wake-ups should be repeated any time the t ref refresh requirement is excee- ded. 3. in addition to meeting the transition rate specification, the clock and cke must transit between v ih and v il (or between v il and v ih ) in a monotonic manner. 4. outputs measured at 1.5v with equivalent load: q 50pf 5. ac operating and i dd test conditions have v il = 0v and v ih = 3.0v using a measurement reference level of 1.5v. if the input transition time is longer than 1ns, then the timing is 256mb: x4, x8, x16 sdram electrical specifications C ac operating conditions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 28 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. measured from v il,max and v ih,min and no longer from the 1.5v midpoint. clk should al- ways be 1.5v referenced to crossover. refer to micron technical note tn-48-09. 6. not applicable for revision d. 7. t ac for -75/-7e at cl = 3 with no load is 4.6ns and is guaranteed by design. 8. the clock frequency must remain constant (stable clock is defined as a signal cycling within timing constraints specified for the clock pin) during access or precharge states (read, write, including t wr, and precharge commands). cke may be used to reduce the data rate. 9. t hz defines the time at which the output achieves the open circuit condition; it is not a reference to v oh or v ol . the last valid data element will meet t oh before going high-z. 10. parameter guaranteed by design. 11. dram devices should be evenly addressed when being accessed. disproportionate ac- cesses to a particular row address may result in reduction of the product lifetime. 12. ac characteristics assume t t = 1ns. 13. auto precharge mode only. the precharge timing budget ( t rp) begins at 6ns for -6a, 7ns for -7e, and 7.5ns for -75 after the first clock delay, after the last write is executed. 14. precharge mode only. 15. clk must be toggled a minimum of two times during this period. 16. required clocks are specified by jedec functionality and are not dependent on any tim- ing parameter. 17. timing is specified by t cks. clock(s) specified as a reference only at minimum cycle rate. 18. timing is specified by t wr plus t rp. clock(s) specified as a reference only at minimum cy- cle rate. 19. based on t ck = 7.5ns for -75 and -7e, 6ns for -6a. 20. timing is specified by t wr. 21. jedec and pc100 specify three clocks. 256mb: x4, x8, x16 sdram electrical specifications C ac operating conditions pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 29 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. functional description in general, 256mb sdram devices (16 meg x 4 x 4 banks, 8 meg x 8 x 4 banks, and 4 meg x 16 x 4 banks) are quad-bank dram that operate at 3.3v and include a synchronous interface. all signals are registered on the positive edge of the clock signal, clk. each of the x4s 67,108,864-bit banks is organized as 8192 rows by 2048 columns by 4 bits. each of the x8s 67,108,864-bit banks is organized as 8192 rows by 1024 columns by 8 bits. each of the x16s 67,108,864-bit banks is organized as 8192 rows by 512 columns by 16 bits. read and write accesses to the sdram are burst-oriented; accesses start at a selected location and continue for a programmed number of locations in a programmed se- quence. accesses begin with the registration of an active command, followed by a read or write command. the address bits registered coincident with the active command are used to select the bank and row to be accessed (ba0 and ba1 select the bank, a[12:0] select the row). the address bits (x4: a[9:0], a11; x8: a[9:0]; x16: a[8:0]) reg- istered coincident with the read or write command are used to select the starting column location for the burst access. prior to normal operation, the sdram must be initialized. the following sections pro- vide detailed information covering device initialization, register definition, command descriptions, and device operation. 256mb: x4, x8, x16 sdram functional description pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 30 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. commands the following table provides a quick reference of available commands, followed by a written description of each command. additional truth tables (table 15 (page 37), ta- ble 16 (page 39), and table 17 (page 41)) provide current state/next state informa- tion. table 14: truth table C commands and dqm operation note 1 applies to all parameters and conditions name (function) cs# ras# cas# we# dqm addr dq notes command inhibit (nop) h x x x x x x no operation (nop) l h h h x x x active (select bank and activate row) l l h h x bank/row x 2 read (select bank and column, and start read burst) l h l h l/h bank/col x 3 write (select bank and column, and start write burst) l h l l l/h bank/col valid 3 burst terminate l h h l x x active 4 precharge (deactivate row in bank or banks) l l h l x code x 5 auto refresh or self refresh (enter self refresh mode) l l l h x x x 6, 7 load mode register l l l l x op-code x 8 write enable/output enable x x x x l x active 9 write inhibit/output high-z x x x x h x high-z 9 notes: 1. cke is high for all commands shown except self refresh. 2. a[0 :n ] provide row address (where a n is the most significant address bit), ba0 and ba1 determine which bank is made active. 3. a[0 :i ] provide column address (where i = the most significant column address for a given device configuration). a10 high enables the auto precharge feature (nonpersistent), while a10 low disables the auto precharge feature. ba0 and ba1 determine which bank is being read from or written to. 4. the purpose of the burst terminate command is to stop a data burst, thus the com- mand could coincide with data on the bus. however, the dq column reads a dont care state to illustrate that the burst terminate command can occur when there is no data present. 5. a10 low: ba0, ba1 determine the bank being precharged. a10 high: all banks pre- charged and ba0, ba1 are dont care. 6. this command is auto refresh if cke is high, self refresh if cke is low. 7. internal refresh counter controls row addressing; all inputs and i/os are dont care ex- cept for cke. 8. a[11:0] define the op-code written to the mode register. 9. activates or deactivates the dq during writes (zero-clock delay) and reads (two-clock delay). command inhibit the command inhibit function prevents new commands from being executed by the device, regardless of whether the clk signal is enabled. the device is effectively de- selected. operations already in progress are not affected. 256mb: x4, x8, x16 sdram commands pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 31 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. no operation (nop) the no operation (nop) command is used to perform a nop to the selected device (cs# is low). this prevents unwanted commands from being registered during idle or wait states. operations already in progress are not affected. load mode register (lmr) the mode registers are loaded via inputs a[ n:0] (where a n is the most significant ad- dress term), ba0, and ba1(see mode register (page 44)). the load mode register command can only be issued when all banks are idle and a subsequent executable com- mand cannot be issued until t mrd is met. active the active command is used to activate a row in a particular bank for a subsequent access. the value on the ba0, ba1 inputs selects the bank, and the address provided se- lects the row. this row remains active for accesses until a precharge command is is- sued to that bank. a precharge command must be issued before opening a different row in the same bank. figure 14: active command cs# we# cas# ras# cke clk address row address dont care high ba0, ba1 bank address 256mb: x4, x8, x16 sdram commands pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 32 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. read the read command is used to initiate a burst read access to an active row. the values on the ba0 and ba1 inputs select the bank; the address provided selects the starting col- umn location. the value on input a10 determines whether auto precharge is used. if au- to precharge is selected, the row being accessed is precharged at the end of the read burst; if auto precharge is not selected, the row remains open for subsequent accesses. read data appears on the dq subject to the logic level on the dqm inputs two clocks earlier. if a given dqm signal was registered high, the corresponding dq will be high- z two clocks later; if the dqm signal was registered low, the dq will provide valid data. figure 15: read command cs# we# cas# ras# cke clk column address a10 1 ba0, ba1 dont care high en ap dis ap bank address address note: 1. en ap = enable auto precharge, dis ap = disable auto precharge. 256mb: x4, x8, x16 sdram commands pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 33 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. write the write command is used to initiate a burst write access to an active row. the values on the ba0 and ba1 inputs select the bank; the address provided selects the starting col- umn location. the value on input a10 determines whether auto precharge is used. if au- to precharge is selected, the row being accessed is precharged at the end of the write burst; if auto precharge is not selected, the row remains open for subsequent accesses. input data appearing on the dq is written to the memory array, subject to the dqm in- put logic level appearing coincident with the data. if a given dqm signal is registered low, the corresponding data is written to memory; if the dqm signal is registered high, the corresponding data inputs are ignored and a write is not executed to that byte/column location. figure 16: write command dis ap en ap cs# we# cas# ras# cke clk column address dont care high bank address address ba0, ba1 valid address a10 1 note: 1. en ap = enable auto precharge, dis ap = disable auto precharge. 256mb: x4, x8, x16 sdram commands pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 34 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. precharge the precharge command is used to deactivate the open row in a particular bank or the open row in all banks. the bank(s) will be available for a subsequent row access a specified time ( t rp) after the precharge command is issued. input a10 determines whether one or all banks are to be precharged, and in the case where only one bank is precharged, inputs ba0 and ba1 select the bank. otherwise ba0 and ba1 are treated as dont care. after a bank has been precharged, it is in the idle state and must be acti- vated prior to any read or write commands are issued to that bank. figure 17: precharge command cs# we# cas# ras# cke clk a10 dont care high all banks bank selected address ba0, ba1 bank address valid address burst terminate the burst terminate command is used to truncate either fixed-length or continu- ous page bursts. the most recently registered read or write command prior to the burst terminate command is truncated. 256mb: x4, x8, x16 sdram commands pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 35 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. refresh auto refresh auto refresh is used during normal operation of the sdram and is analogous to cas#-before-ras# (cbr) refresh in conventional drams. this command is nonper- sistent, so it must be issued each time a refresh is required. all active banks must be pre- charged prior to issuing an auto refresh command. the auto refresh command should not be issued until the minimum t rp has been met after the precharge com- mand, as shown in bank/row activation (page 49). the addressing is generated by the internal refresh controller. this makes the address bits a dont care during an auto refresh command. regardless of device width, the 256mb sdram requires 8192 auto refresh cycles every 64ms (commercial and industrial) or 16ms (automotive). providing a distributed auto refresh command every 7.813 s (commercial and industrial) or 1.953 s (automotive) will meet the refresh requirement and ensure that each row is refreshed. alternatively, 8192 auto refresh commands can be issued in a burst at the minimum cycle rate ( t rfc), once every 64ms (commercial and industrial) or 16ms (automotive). self refresh the self refresh command can be used to retain data in the sdram, even if the rest of the system is powered-down. when in the self refresh mode, the sdram retains data without external clocking. the self refresh command is initiated like an auto refresh command except cke is disabled (low). after the self refresh command is registered, all the inputs to the sdram become a dont care with the exception of cke, which must remain low. after self refresh mode is engaged, the sdram provides its own internal clocking, caus- ing it to perform its own auto refresh cycles. the sdram must remain in self re- fresh mode for a minimum period equal to t ras and may remain in self refresh mode for an indefinite period beyond that. the procedure for exiting self refresh requires a sequence of commands. first, clk must be stable (stable clock is defined as a signal cycling within timing constraints specified for the clock pin) prior to cke going back high. after cke is high, the sdram must have nop commands issued (a minimum of two clocks) for t xsr because time is required for the completion of any internal refresh in progress. upon exiting the self refresh mode, auto refresh commands must be issued at the specified intervals, as both self refresh and auto refresh utilize the row refresh counter. self refresh is not supported on automotive temperature devices. 256mb: x4, x8, x16 sdram commands pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 36 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. truth tables table 15: truth table C current state bank n , command to bank n notes 1C6 apply to all parameters and conditions current state cs# ras# cas# we# command/action notes any h x x x command inhibit (nop/continue previous operation) l h h h no operation (nop/continue previous operation) idle l l h h active (select and activate row) l l l h auto refresh 7 l l l l load mode register 7 l l h l precharge 8 row active l h l h read (select column and start read burst) 9 l h l l write (select column and start write burst) 9 l l h l precharge (deactivate row in bank or banks) 10 read (auto precharge disabled) l h l h read (select column and start new read burst) 9 l h l l write (select column and start write burst) 9 l l h l precharge (truncate read burst, start precharge) 10 l h h l burst terminate 11 write (auto precharge disabled) l h l h read (select column and start read burst) 9 l h l l write (select column and start new write burst) 9 l l h l precharge (truncate write burst, start precharge) 10 l h h l burst terminate 11 notes: 1. this table applies when cke n-1 was high and cke n is high (see table 17 (page 41)) and after t xsr has been met (if the previous state was self refresh). 2. this table is bank-specific, except where noted (for example, the current state is for a specific bank and the commands shown can be issued to that bank when in that state). exceptions are covered below. 3. current state definitions: idle : the bank has been precharged, and t rp has been met. row active : a row in the bank has been activated, and t rcd has been met. no data bursts/accesses and no register accesses are in progress. read : a read burst has been initiated, with auto precharge disabled, and has not yet terminated or been terminated. write : a write burst has been initiated, with auto precharge disabled, and has not yet terminated or been terminated. 4. the following states must not be interrupted by a command issued to the same bank. command inhibit or nop commands, or supported commands to the other bank should be issued on any clock edge occurring during these states. supported commands to any other bank are determined by the banks current state and the conditions descri- bed in this and the following table. precharging : starts with registration of a precharge command and ends when t rp is met. after t rp is met, the bank will be in the idle state. row activating : starts with registration of an active command and ends when t rcd is met. after t rcd is met, the bank will be in the row active state. 256mb: x4, x8, x16 sdram truth tables pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 37 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. read with auto precharge enabled : starts with registration of a read command with auto precharge enabled and ends when t rp has been met. after t rp is met, the bank will be in the idle state. write with auto precharge enabled : starts with registration of a write command with auto precharge enabled and ends when t rp has been met. after t rp is met, the bank will be in the idle state. 5. the following states must not be interrupted by any executable command; command inhibit or nop commands must be applied on each positive clock edge during these states. refreshing : starts with registration of an auto refresh command and ends when t rfc is met. after t rfc is met, the device will be in the all banks idle state. accessing mode register : starts with registration of a load mode register com- mand and ends when t mrd has been met. after t mrd is met, the device will be in the all banks idle state. precharging all : starts with registration of a precharge all command and ends when t rp is met. after t rp is met, all banks will be in the idle state. 6. all states and sequences not shown are illegal or reserved. 7. not bank specific; requires that all banks are idle. 8. does not affect the state of the bank and acts as a nop to that bank. 9. reads or writes listed in the command/action column include reads or writes with auto precharge enabled and reads or writes with auto precharge disabled. 10. may or may not be bank specific; if all banks need to be precharged, each must be in a valid state for precharging. 11. not bank-specific; burst terminate affects the most recent read or write burst, re- gardless of bank. 256mb: x4, x8, x16 sdram truth tables pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 38 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. table 16: truth table C current state bank n, command to bank m notes 1C6 apply to all parameters and conditions current state cs# ras# cas# we# command/action notes any h x x x command inhibit (nop/continue previous operation) l h h h no operation (nop/continue previous operation) idle x x x x any command otherwise supported for bank m row activating, active, or precharging l l h h active (select and activate row) l h l h read (select column and start read burst) 7 l h l l write (select column and start write burst) 7 l l h l precharge read (auto precharge disabled) l l h h active (select and activate row) l h l h read (select column and start new read burst) 7, 10 l h l l write (select column and start write burst) 7, 11 l l h l precharge 9 write (auto precharge disabled) l l h h active (select and activate row) l h l h read (select column and start read burst) 7, 12 l h l l write (select column and start new write burst) 7, 13 l l h l precharge 9 read (with auto precharge) l l h h active (select and activate row) l h l h read (select column and start new read burst) 7, 8, 14 l h l l write (select column and start write burst) 7, 8, 15 l l h l precharge 9 write (with auto precharge) l l h h active (select and activate row) l h l h read (select column and start read burst) 7, 8, 16 l h l l write (select column and start new write burst) 7, 8, 17 l l h l precharge 9 notes: 1. this table applies when cke n-1 was high and cke n is high (table 17 (page 41)), and after t xsr has been met (if the previous state was self refresh). 2. this table describes alternate bank operation, except where noted; for example, the cur- rent state is for bank n and the commands shown can be issued to bank m , assuming that bank m is in such a state that the given command is supported. exceptions are cov- ered below. 3. current state definitions: idle : the bank has been precharged, and t rp has been met. row active : a row in the bank has been activated, and t rcd has been met. no data bursts/accesses and no register accesses are in progress. read : a read burst has been initiated, with auto precharge disabled, and has not yet terminated or been terminated. write : a write burst has been initiated, with auto precharge disabled, and has not yet terminated or been terminated. 256mb: x4, x8, x16 sdram truth tables pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 39 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. read with auto precharge enabled : starts with registration of a read command with auto precharge enabled and ends when t rp has been met. after t rp is met, the bank will be in the idle state. write with auto precharge enabled : starts with registration of a write command with auto precharge enabled and ends when t rp has been met. after t rp is met, the bank will be in the idle state. 4. auto refresh, self refresh, and load mode register commands can only be is- sued when all banks are idle. 5. a burst terminate command cannot be issued to another bank; it applies to the bank represented by the current state only. 6. all states and sequences not shown are illegal or reserved. 7. reads or writes to bank m listed in the command/action column include reads or writes with auto precharge enabled and reads or writes with auto precharge disa- bled. 8. concurrent auto precharge: bank n will initiate the auto precharge command when its burst has been interrupted by bank m burst. 9. the burst in bank n continues as initiated. 10. for a read without auto precharge interrupted by a read (with or without auto pre- charge), the read to bank m will interrupt the read on bank n , cas latency (cl) later. 11. for a read without auto precharge interrupted by a write (with or without auto pre- charge), the write to bank m will interrupt the read on bank n when registered. dqm should be used one clock prior to the write command to prevent bus contention. 12. for a write without auto precharge interrupted by a read (with or without auto pre- charge), the read to bank m will interrupt the write on bank n when registered, with the data-out appearing cl later. the last valid write to bank n will be data-in regis- tered one clock prior to the read to bank m . 13. for a write without auto precharge interrupted by a write (with or without auto pre- charge), the write to bank m will interrupt the write on bank n when registered. the last valid write to bank n will be data-in registered one clock prior to the read to bank m . 14. for a read with auto precharge interrupted by a read (with or without auto pre- charge), the read to bank m will interrupt the read on bank n , cl later. the pre- charge to bank n will begin when the read to bank m is registered. 15. for a read with auto precharge interrupted by a write (with or without auto pre- charge), the write to bank m will interrupt the read on bank n when registered. dqm should be used two clocks prior to the write command to prevent bus contention. the precharge to bank n will begin when the write to bank m is registered. 16. for a write with auto precharge interrupted by a read (with or without auto pre- charge), the read to bank m will interrupt the write on bank n when registered, with the data-out appearing cl later. the precharge to bank n will begin after t wr is met, where t wr begins when the read to bank m is registered. the last valid write bank n will be data-in registered one clock prior to the read to bank m . 17. for a write with auto precharge interrupted by a write (with or without auto pre- charge), the write to bank m will interrupt the write on bank n when registered. the precharge to bank n will begin after t wr is met, where t wr begins when the write to bank m is registered. the last valid write to bank n will be data registered one clock to the write to bank m . 256mb: x4, x8, x16 sdram truth tables pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 40 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. table 17: truth table C cke notes 1C4 apply to all parameters and conditions current state cke n-1 cke n command n action n notes power-down l l x maintain power-down self refresh x maintain self refresh clock suspend x maintain clock suspend power-down l h command inhibit or nop exit power-down 5 self refresh command inhibit or nop exit self refresh 6 clock suspend x exit clock suspend 7 all banks idle h l command inhibit or nop power-down entry all banks idle auto refresh self refresh entry reading or writing valid clock suspend entry h h see table 16 (page 39). notes: 1. cke n is the logic state of cke at clock edge n; cke n-1 was the state of cke at the previ- ous clock edge. 2. current state is the state of the sdram immediately prior to clock edge n . 3. command n is the command registered at clock edge n , and action n is a result of command n . 4. all states and sequences not shown are illegal or reserved. 5. exiting power-down at clock edge n will put the device in the all banks idle state in time for clock edge n + 1 (provided that t cks is met). 6. exiting self refresh at clock edge n will put the device in the all banks idle state after t xsr is met. command inhibit or nop commands should be issued on any clock edges occurring during the t xsr period. a minimum of two nop commands must be provided during the t xsr period. 7. after exiting clock suspend at clock edge n , the device will resume operation and recog- nize the next command at clock edge n + 1. 256mb: x4, x8, x16 sdram truth tables pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 41 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. initialization sdram must be powered up and initialized in a predefined manner. operational proce- dures other than those specified may result in undefined operation. after power is ap- plied to v dd and v ddq (simultaneously) and the clock is stable (stable clock is defined as a signal cycling within timing constraints specified for the clock pin), the sdram re- quires a 100 s delay prior to issuing any command other than a command inhibit or nop. starting at some point during this 100 s period and continuing at least through the end of this period, command inhibit or nop commands must be applied. after the 100 s delay has been satisfied with at least one command inhibit or nop command having been applied, a precharge command should be applied. all banks must then be precharged, thereby placing the device in the all banks idle state. once in the idle state, at least two auto refresh cycles must be performed. after the auto refresh cycles are complete, the sdram is ready for mode register program- ming. because the mode register will power up in an unknown state, it must be loaded prior to applying any operational command. if desired, the two auto refresh com- mands can be issued after the lmr command. the recommended power-up sequence for sdram: 1. simultaneously apply power to v dd and v ddq . 2. assert and hold cke at a lvttl logic low since all inputs and outputs are lvttl- compatible. 3. provide stable clock signal. stable clock is defined as a signal cycling within tim- ing constraints specified for the clock pin. 4. wait at least 100 s prior to issuing any command other than a command inhib- it or nop. 5. starting at some point during this 100 s period, bring cke high. continuing at least through the end of this period, 1 or more command inhibit or nop com- mands must be applied. 6. perform a precharge all command. 7. wait at least t rp time; during this time nops or deselect commands must be given. all banks will complete their precharge, thereby placing the device in the all banks idle state. 8. issue an auto refresh command. 9. wait at least t rfc time, during which only nops or command inhibit com- mands are allowed. 10. issue an auto refresh command. 11. wait at least t rfc time, during which only nops or command inhibit com- mands are allowed. 12. the sdram is now ready for mode register programming. because the mode reg- ister will power up in an unknown state, it should be loaded with desired bit values prior to applying any operational command. using the lmr command, program the mode register. the mode register is programmed via the mode register set command with ba1 = 0, ba0 = 0 and retains the stored information until it is pro- grammed again or the device loses power. not programming the mode register upon initialization will result in default settings which may not be desired. out- puts are guaranteed high-z after the lmr command is issued. outputs should be high-z already before the lmr command is issued. 13. wait at least t mrd time, during which only nop or deselect commands are al- lowed. at this point the dram is ready for any valid command. 256mb: x4, x8, x16 sdram initialization pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 42 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. note: more than two auto refresh commands can be issued in the sequence. after steps 9 and 10 are complete, repeat them until the desired number of auto refresh + t rfc loops is achieved. figure 18: initialize and load mode register t ch t cl t ck cke ck command dq ba[1:0] t rfc t mrd t rfc auto refresh auto refresh program mode register 1,3,4 t cmh t cms precharge all banks ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) t rp ( ) ( ) ( ) ( ) t cks power-up: v dd and clk stable t = 100s min precharge auto refresh load mode register active ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) auto refresh all banks ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) high-z t ckh ( ) ( ) ( ) ( ) dqm/dqml, dqmu ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) nop 2 nop 2 nop 2 nop 2 ( ) ( ) ( ) ( ) a[9:0], a[12:11] row t ah 5 t as t ah t as code ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) a10 row code ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) all banks single bank ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) dont care undefined t0 t1 tn + 1 to + 1 tp + 1 tp + 2 tp + 3 notes: 1. the mode register may be loaded prior to the auto refresh cycles if desired. 2. if cs is high at clock high time, all commands applied are nop. 3. jedec and pc100 specify three clocks. 4. outputs are guaranteed high-z after command is issued. 5. a12 should be a low at t p + 1. 256mb: x4, x8, x16 sdram initialization pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 43 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. mode register the mode register defines the specific mode of operation, including burst length (bl), burst type, cas latency (cl), operating mode, and write burst mode. the mode register is programmed via the load mode register command and retains the stored infor- mation until it is programmed again or the device loses power. mode register bits m[2:0] specify the bl; m3 specifies the type of burst; m[6:4] specify the cl; m7 and m8 specify the operating mode; m9 specifies the write burst mode; and m10Cm n should be set to zero to ensure compatibility with future revisions. m n + 1 and m n + 2 should be set to zero to select the mode register. the mode registers must be loaded when all banks are idle, and the controller must wait t mrd before initiating the subsequent operation. violating either of these requirements will result in unspecified operation. 256mb: x4, x8, x16 sdram mode register pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 44 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 19: mode register definition m3 = 0 1 2 4 8 reserved reserved reserved full page m3 = 1 1 2 4 8 reserved reserved reserved reserved operating mode standard operation all other states reserved 0 C 0 C defined C 0 1 burst type sequential interleaved cas latency reserved 1 2 3 reserved reserved reserved reserved burst length m0 0 1 0 1 0 1 0 1 burst length cas latency bt a9 a7 a6 a5 a4 a3 a8 a2 a1 a0 mode register (mx) address bus 7 6 5 4 3 8 2 1 0 m1 0 0 1 1 0 0 1 1 m2 0 0 0 0 1 1 1 1 m3 m4 0 1 0 1 0 1 0 1 m5 0 0 1 1 0 0 1 1 m6 0 0 0 0 1 1 1 1 m6-m0 m8 m7 op mode a10 a11 10 11 reserved wb 0 1 write burst mode programmed burst length single location access m9 program ba1, ba0 = 0, 0 to ensure compatibility with future devices. a12 12 9 256mb: x4, x8, x16 sdram mode register pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 45 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. burst length read and write accesses to the device are burst oriented, and the burst length (bl) is programmable. the burst length determines the maximum number of column loca- tions that can be accessed for a given read or write command. burst lengths of 1, 2, 4, 8, or continuous locations are available for both the sequential and the interleaved burst types, and a continuous page burst is available for the sequential type. the con- tinuous page burst is used in conjunction with the burst terminate command to generate arbitrary burst lengths. reserved states should not be used, as unknown operation or incompatibility with fu- ture versions may result. when a read or write command is issued, a block of columns equal to the burst length is effectively selected. all accesses for that burst take place within this block, meaning that the burst wraps within the block when a boundary is reached. the block is uniquely selected by a[8:1] when bl = 2, a[8:2] when bl = 4, and a[8:3] when bl = 8. the remaining (least significant) address bit(s) is (are) used to select the starting loca- tion within the block. continuous page bursts wrap within the page when the boundary is reached. burst type accesses within a given burst can be programmed to be either sequential or interleaved; this is referred to as the burst type and is selected via bit m3. the ordering of accesses within a burst is determined by the burst length, the burst type, and the starting column address. 256mb: x4, x8, x16 sdram mode register pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 46 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. table 18: burst definition table burst length starting column address order of accesses within a burst type = sequential type = interleaved 2 a0 0 0-1 0-1 1 1-0 1-0 4 a1 a0 0 0 0-1-2-3 0-1-2-3 0 1 1-2-3-0 1-0-3-2 1 0 2-3-0-1 2-3-0-1 1 1 3-0-1-2 3-2-1-0 8 a2 a1 a0 0 0 0 0-1-2-3-4-5-6-7 0-1-2-3-4-5-6-7 0 0 1 1-2-3-4-5-6-7-0 1-0-3-2-5-4-7-6 0 1 0 2-3-4-5-6-7-0-1 2-3-0-1-6-7-4-5 0 1 1 3-4-5-6-7-0-1-2 3-2-1-0-7-6-5-4 1 0 0 4-5-6-7-0-1-2-3 4-5-6-7-0-1-2-3 1 0 1 5-6-7-0-1-2-3-4 5-4-7-6-1-0-3-2 1 1 0 6-7-0-1-2-3-4-5 6-7-4-5-2-3-0-1 1 1 1 7-0-1-2-3-4-5-6 7-6-5-4-3-2-1-0 continuous n = a0Can/9/8 (location 0Cy) cn, cn + 1, cn + 2, cn + 3...cn - 1, cn... not supported notes: 1. for full-page accesses: y = 2048 (x4); y = 1024 (x8); y = 512 (x16). 2. for bl = 2, a1Ca9, a11 (x4); a1Ca9 (x8); or a1Ca8 (x16) select the block-of-two burst; a0 selects the starting column within the block. 3. for bl = 4, a2Ca9, a11 (x4); a2Ca9 (x8); or a2Ca8 (x16) select the block-of-four burst; a0Ca1 select the starting column within the block. 4. for bl = 8, a3Ca9, a11 (x4); a3Ca9 (x8); or a3Ca8 (x16) select the block-of-eight burst; a0Ca2 select the starting column within the block. 5. for a full-page burst, the full row is selected and a0Ca9, a11 (x4); a0Ca9 (x8); or a0Ca8 (x16) select the starting column. 6. whenever a boundary of the block is reached within a given sequence above, the fol- lowing access wraps within the block. 7. for bl = 1, a0Ca9, a11 (x4); a0Ca9 (x8); or a0Ca8 (x16) select the unique column to be accessed, and mode register bit m3 is ignored. 256mb: x4, x8, x16 sdram mode register pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 47 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. cas latency the cas latency (cl) is the delay, in clock cycles, between the registration of a read command and the availability of the output data. the latency can be set to two or three clocks. if a read command is registered at clock edge n , and the latency is m clocks, the data will be available by clock edge n + m . the dq start driving as a result of the clock edge one cycle earlier ( n + m - 1), and provided that the relevant access times are met, the data is valid by clock edge n + m . for example, assuming that the clock cycle time is such that all relevant access times are met, if a read command is registered at t0 and the latency is programmed to two clocks, the dq start driving after t1 and the data is valid by t2. reserved states should not be used as unknown operation or incompatibility with fu- ture versions may result. figure 20: cas latency clk dq t2 t1 t3 t0 cl = 3 t lz d out t oh command nop read nop t4 nop dont care undefined clk dq t2 t1 t3 t0 cl = 2 t lz d out t oh command nop read t ac t ac nop operating mode the normal operating mode is selected by setting m7 and m8 to zero; the other combi- nations of values for m7 and m8 are reserved for future use. reserved states should not be used because unknown operation or incompatibility with future versions may result. write burst mode when m9 = 0, the burst length programmed via m[2:0] applies to both read and write bursts; when m9 = 1, the programmed burst length applies to read bursts, but write accesses are single-location (nonburst) accesses. 256mb: x4, x8, x16 sdram mode register pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 48 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. bank/row activation before any read or write commands can be issued to a bank within the sdram, a row in that bank must be opened. this is accomplished via the active command, which selects both the bank and the row to be activated. after a row is opened with the active command, a read or write command can be issued to that row, subject to the t rcd specification. t rcd (min) should be divided by the clock period and rounded up to the next whole number to determine the earliest clock edge after the active command on which a read or write command can be entered. for example, a t rcd specification of 20ns with a 125 mhz clock (8ns period) results in 2.5 clocks, rounded to 3. this is reflected in figure 21 (page 49), which covers any case where 2 < t rcd (min)/ t ck 3. (the same procedure is used to convert other specification limits from time units to clock cycles.) a subsequent active command to a different row in the same bank can only be issued after the previous active row has been precharged. the minimum time interval between successive active commands to the same bank is defined by t rc. a subsequent active command to another bank can be issued while the first bank is being accessed, which results in a reduction of total row-access overhead. the mini- mum time interval between successive active commands to different banks is defined by t rrd. figure 21: example: meeting t rcd (min) when 2 < t rcd (min)/ t ck < 3 clk t2 t1 t3 t0 t command nop active read or write nop rcd(min) t ck t ck t ck dont care 256mb: x4, x8, x16 sdram bank/row activation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 49 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. read operation read bursts are initiated with a read command, as shown in figure 15 (page 33). the starting column and bank addresses are provided with the read command, and auto precharge is either enabled or disabled for that burst access. if auto precharge is ena- bled, the row being accessed is precharged at the completion of the burst. in the follow- ing figures, auto precharge is disabled. during read bursts, the valid data-out element from the starting column address is available following the cas latency after the read command. each subsequent data- out element will be valid by the next positive clock edge. figure 23 (page 52) shows general timing for each possible cas latency setting. upon completion of a burst, assuming no other commands have been initiated, the dq signals will go to high-z. a continuous page burst continues until terminated. at the end of the page, it wraps to column 0 and continues. data from any read burst can be truncated with a subsequent read command, and data from a fixed-length read burst can be followed immediately by data from a read command. in either case, a continuous flow of data can be maintained. the first data element from the new burst either follows the last element of a completed burst or the last desired data element of a longer burst that is being truncated. the new read com- mand should be issued x cycles before the clock edge at which the last desired data ele- ment is valid, where x = cl - 1. this is shown in figure 23 (page 52) for cl2 and cl3. sdram devices use a pipelined architecture and therefore do not require the 2 n rule as- sociated with a prefetch architecture. a read command can be initiated on any clock cycle following a read command. full-speed random read accesses can be performed to the same bank, or each subsequent read can be performed to a different bank. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 50 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 22: consecutive read bursts dont care clk dq d out n t2 t1 t4 t3 t6 t5 t0 command address read nop nop nop nop bank, col n nop bank, col b d out n + 1 d out n + 2 d out n + 3 d out b read x = 1 cycle cl = 2 clk dq d out t2 t1 t4 t3 t6 t5 t0 command address read nop nop nop nop bank, col n nop bank, col b d out d out d out d out read nop t7 cl = 3 transitioning data x = 2 cycles note: 1. each read command can be issued to any bank. dqm is low. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 51 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 23: random read accesses clk dq t2 t1 t4 t3 t6 t5 t0 command address dont care d out d out d out d out clk dq t2 t1 t4 t3 t5 t0 command address read nop bank, col n read read read nop bank, col a bank, col x bank, col m read nop bank, col n bank, col a read read read nop nop bank, col x bank, col m cl = 2 cl = 3 d out d out d out d out transitioning data note: 1. each read command can be issued to any bank. dqm is low. data from any read burst can be truncated with a subsequent write command, and data from a fixed-length read burst can be followed immediately by data from a write command (subject to bus turnaround limitations). the write burst can be ini- tiated on the clock edge immediately following the last (or last desired) data element from the read burst, provided that i/o contention can be avoided. in a given system design, there is a possibility that the device driving the input data will go low-z before the dq go high-z. in this case, at least a single-cycle delay should occur between the last read data and the write command. the dqm input is used to avoid i/o contention, as shown in figure 24 (page 53) and figure 25 (page 54). the dqm signal must be asserted (high) at least two clocks prior to the write command (dqm latency is two clocks for output buffers) to suppress da- ta-out from the read. after the write command is registered, the dq will go to high-z (or remain high-z), regardless of the state of the dqm signal, provided the dqm was active on the clock just prior to the write command that truncated the read com- mand. if not, the second write will be an invalid write. for example, if dqm was low during t4, then the writes at t5 and t7 would be valid, and the write at t6 would be invalid. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 52 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. the dqm signal must be de-asserted prior to the write command (dqm latency is zero clocks for input buffers) to ensure that the written data is not masked. figure 24 (page 53) shows where, due to the clock cycle frequency, bus contention is avoided without having to add a nop cycle, while figure 25 (page 54) shows the case where an additional nop cycle is required. a fixed-length read burst may be followed by or truncated with a precharge com- mand to the same bank, provided that auto precharge was not activated. the pre- charge command should be issued x cycles before the clock edge at which the last de- sired data element is valid, where x = cl - 1. this is shown in figure 26 (page 54) for each possible cl; data element n + 3 is either the last of a burst of four or the last de- sired data element of a longer burst. following the precharge command, a subse- quent command to the same bank cannot be issued until t rp is met. note that part of the row precharge time is hidden during the access of the last data element(s). in the case of a fixed-length burst being executed to completion, a precharge com- mand issued at the optimum time (as described above) provides the same operation that would result from the same fixed-length burst with auto precharge. the disadvant- age of the precharge command is that it requires that the command and address buses be available at the appropriate time to issue the command. the advantage of the precharge command is that it can be used to truncate fixed-length or continuous page bursts. figure 24: read-to-write read nop nop write nop clk t2 t1 t4 t3 t0 dqm dq command address bank, col b bank, col n ds t hz t ck dont care transitioning data t d out d in note: 1. cl = 3. the read command can be issued to any bank, and the write command can be to any bank. if a burst of one is used, dqm is not required. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 53 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 25: read-to-write with extra clock cycle dont care read nop nop nop nop dqm clk dq d out t2 t1 t4 t3 t0 command address bank, col n write d in bank, col b t5 t ds t hz transitioning data note: 1. cl = 3. the read command can be issued to any bank, and the write command can be to any bank. figure 26: read-to-precharge dont care clk dq t2 t1 t4 t3 t6 t5 t0 command address read nop nop nop nop nop precharge active t rp t7 clk dq d out t2 t1 t4 t3 t6 t5 t0 command address read nop nop nop nop nop d out d out d out precharge active t rp t7 x = 1 cycle cl = 2 cl = 3 x = 2 cycles bank a , col n bank a , row bank ( a or all) bank a , col bank a , row bank ( a or all) transitioning data d out d out d out d out note: 1. dqm is low. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 54 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. continuous-page read bursts can be truncated with a burst terminate command and fixed-length read bursts can be truncated with a burst terminate command, provided that auto precharge was not activated. the burst terminate command should be issued x cycles before the clock edge at which the last desired data element is valid, where x = cl - 1. this is shown in figure 27 (page 55) for each possible cas la- tency; data element n + 3 is the last desired data element of a longer burst. figure 27: terminating a read burst clk dq t2 t1 t4 t3 t6 t5 t0 command address nop nop nop nop nop burst terminate nop t7 clk dq d out t2 t1 t4 t3 t6 t5 t0 command address read nop nop nop nop d out d out d out burst terminate nop x = 1 cycle cl = 2 cl = 3 x = 2 cycles dont care transitioning data bank, col n read bank, col n d out d out d out d out note: 1. dqm is low. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 55 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 28: alternating bank read accesses dont care undefined enable auto precharge t ch t cl t ck t ac t lz clk dq a10 t oh d out t cmh t cms t ah t as t ah t as t ah t as row row row row t oh d out t ac t oh t ac t oh t ac d out d out command t cmh t cms nop nop active nop read nop active t oh d out t ac t ac read enable auto precharge row active row bank 0 bank 0 bank 3 bank 3 bank 0 cke t ckh t cks column m column b 1 t0 t1 t2 t4 t3 t5 t6 t7 t8 t rp - bank 0 t ras - bank 0 t rcd - bank 0 t rcd - bank 0 cl - bank 0 t rcd - bank 3 cl - bank 3 t rc - bank 0 t rrd ba0, ba1 dqm address note: 1. for this example, bl = 4 and cl = 2. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 56 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 29: read continuous page burst t ch t cl t ck t ac t lz t rcd cas latency cke clk dq a10 t oh d out t cmh t cms t ah t as t ah t as t ac t oh d out row row t hz t ac t oh d out t ac t oh d out t ac t oh d out t ac t oh d out ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) full page completed all locations within same row dont care undefined command t cmh t cms nop nop nop active nop read nop burst term nop nop ( ) ( ) ( ) ( ) nop ( ) ( ) ( ) ( ) t ah t as bank ( ) ( ) ( ) ( ) bank t ckh t cks ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) column m t0 t1 t2 t4 t3 t5 t6 tn + 1 tn + 2 tn + 3 tn + 4 ba0, ba1 dqm address full-page burst does not self-terminate. can use burst terminate command. note: 1. for this example, cl = 2. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 57 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 30: read C dqm operation t ch t cl t ck t ac t ac t lz t rcd cl = 2 cke clk dq a10 t oh d out t cmh t cms t ah t as t ah t as t ah t as row bank row bank t hz t ac t lz t oh d out t oh d out t hz command t cmh t cms nop nop nop nop active nop read nop nop disable auto precharge enable auto precharge dont care undefined t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 ba0, ba1 dqm address note: 1. for this example, bl = 4 and cl = 2. 256mb: x4, x8, x16 sdram read operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 58 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. write operation write bursts are initiated with a write command, as shown in figure 16 (page 34). the starting column and bank addresses are provided with the write command and auto precharge is either enabled or disabled for that access. if auto precharge is ena- bled, the row being accessed is precharged at the completion of the burst. for the ge- neric write commands used in the following figures, auto precharge is disabled. during write bursts, the first valid data-in element is registered coincident with the write command. subsequent data elements are registered on each successive positive clock edge. upon completion of a fixed-length burst, assuming no other commands have been initiated, the dq will remain at high-z and any additional input data will be ignored (see figure 31 (page 59)). a continuous page burst continues until terminated; at the end of the page, it wraps to column 0 and continues. data for any write burst can be truncated with a subsequent write command, and data for a fixed-length write burst can be followed immediately by data for a write command. the new write command can be issued on any clock following the previ- ous write command, and the data provided coincident with the new command ap- plies to the new command (see figure 32 (page 60)). data n + 1 is either the last of a burst of two or the last desired data element of a longer burst. sdram devices use a pipelined architecture and therefore do not require the 2 n rule as- sociated with a prefetch architecture. a write command can be initiated on any clock cycle following a previous write command. full-speed random write accesses within a page can be performed to the same bank, as shown in figure 33 (page 61), or each subsequent write can be performed to a different bank. figure 31: write burst clk dq d in t2 t1 t3 t0 command address nop nop dont care write d in nop bank, col n transitioning data note: 1. bl = 2. dqm is low. 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 59 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 32: write-to-write clk dq t2 t1 t0 command address nop write write bank, col n bank, col b d in d in d in dont care transitioning data note: 1. dqm is low. each write command may be issued to any bank. data for any write burst can be truncated with a subsequent read command, and data for a fixed-length write burst can be followed immediately by a read command. after the read command is registered, data input is ignored and writes will not be executed (see figure 34 (page 61)). data n + 1 is either the last of a burst of two or the last desired data element of a longer burst. data for a fixed-length write burst can be followed by or truncated with a pre- charge command to the same bank, provided that auto precharge was not activated. a continuous-page write burst can be truncated with a precharge command to the same bank. the precharge command should be issued t wr after the clock edge at which the last desired input data element is registered. the auto precharge mode re- quires a t wr of at least one clock with time to complete, regardless of frequency. in addition, when truncating a write burst at high clock frequencies ( t ck < 15ns), the dqm signal must be used to mask input data for the clock edge prior to and the clock edge coincident with the precharge command (see figure 35 (page 62)). data n + 1 is either the last of a burst of two or the last desired data element of a longer burst. fol- lowing the precharge command, a subsequent command to the same bank cannot be issued until t rp is met. in the case of a fixed-length burst being executed to completion, a precharge com- mand issued at the optimum time (as described above) provides the same operation that would result from the same fixed-length burst with auto precharge. the disadvant- age of the precharge command is that it requires that the command and address buses be available at the appropriate time to issue the command. the advantage of the precharge command is that it can be used to truncate fixed-length bursts or continu- ous page bursts. 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 60 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 33: random write cycles dont care clk dq d in t2 t1 t3 t0 command address write bank, col n d in d in d in write write write bank, col a bank, col x bank, col m transitioning data note: 1. each write command can be issued to any bank. dqm is low. figure 34: write-to-read dont care clk dq t2 t1 t3 t0 command address nop write bank, col n d in d in d out read nop nop bank, col b nop d out t4 t5 transitioning data note: 1. the write command can be issued to any bank, and the read command can be to any bank. dqm is low. cl = 2 for illustration. 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 61 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 35: write-to-precharge dont care dqm clk dq t2 t1 t4 t3 t0 command address bank a, col n t5 nop write precharge nop nop d in d in active t rp bank (a or all) t wr bank a, row dqm dq command address bank a, col n nop write precharge nop nop active t rp bank (a or all) t wr bank a, row t6 nop nop t wr @ t ck < 15ns t wr @ t ck 15ns d in d in transitioning data note: 1. in this example dqm could remain low if the write burst is a fixed length of two. fixed-length write bursts can be truncated with the burst terminate command. when truncating a write burst, the input data applied coincident with the burst terminate command is ignored. the last data written (provided that dqm is low at that time) will be the input data applied one clock previous to the burst terminate command. this is shown in figure 36 (page 63), where data n is the last desired data element of a longer burst. 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 62 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 36: terminating a write burst dont care clk dq t2 t1 t0 command address bank, col n write burst terminate next command d in address data transitioning data note: 1. dqm is low. 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 63 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 37: alternating bank write accesses dont care enable auto precharge t ch t cl t ck clk dq a10 t cmh t cms t ah t as t ah t as t ah t as row row row row command t cmh t cms nop nop active nop write nop nop active write enable auto precharge row active row bank 0 bank 0 bank 1 bank 1 bank 0 cke t ckh t cks column m column b t0 t1 t2 t4 t3 t5 t6 t7 t8 t9 t rp - bank 0 t ras - bank 0 t rcd - bank 0 t rcd - bank 0 t wr - bank 1 t wr - bank 0 t rcd - bank 1 t rc - bank 0 t rrd ba0, ba1 dqm address d in t dh t ds d in d in d in t dh t ds t dh t ds t dh t ds d in t dh t ds d in t dh t ds d in t dh t ds d in t dh t ds note: 1. for this example, bl = 4. 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 64 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 38: write C continuous page burst t ch t cl t ck t rcd cke clk a10 t cms t ah t as t ah t as row row full-page burst does not self-terminate. use burst terminate command to stop. 1, 2 ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) full page completed dont care command t cmh t cms nop nop nop active nop write burst term nop nop ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) dq d in t dh t ds d in d in d in t dh t ds t dh t ds t dh t ds d in t dh t ds t ah t as bank ( ) ( ) ( ) ( ) bank t cmh t ckh t cks ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) all locations within same row column m t0 t1 t2 t3 t4 t5 tn + 1 tn + 2 tn + 3 ba0, ba1 dqm address notes: 1. t wr must be satisfied prior to issuing a precharge command. 2. page left open; no t rp. 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 65 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 39: write C dqm operation dont care t ch t cl t ck t rcd cke clk dq a10 t cms t ah t as row bank row bank enable auto precharge d in t dh t ds d in d in t cmh command nop nop nop active nop write nop nop t cms t cmh t dh t ds t dh t ds t ah t as t ah t as disable auto precharge t ckh t cks column m t0 t1 t2 t3 t4 t5 t6 t7 ba0, ba1 dqm address note: 1. for this example, bl = 4. burst read/single write the burst read/single write mode is entered by programming the write burst mode bit (m9) in the mode register to a 1. in this mode, all write commands result in the access of a single column location (burst of one), regardless of the programmed burst length. read commands access columns according to the programmed burst length and se- quence, just as in the normal mode of operation (m9 = 0). 256mb: x4, x8, x16 sdram write operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 66 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. precharge operation the precharge command (see figure 17 (page 35)) is used to deactivate the open row in a particular bank or the open row in all banks. the bank(s) will be available for a sub- sequent row access some specified time ( t rp) after the precharge command is is- sued. input a10 determines whether one or all banks are to be precharged, and in the case where only one bank is to be precharged (a10 = low), inputs ba0 and ba1 select the bank. when all banks are to be precharged (a10 = high), inputs ba0 and ba1 are treated as dont care. after a bank has been precharged, it is in the idle state and must be activated prior to any read or write commands being issued to that bank. auto precharge auto precharge is a feature that performs the same individual-bank precharge func- tion described previously, without requiring an explicit command. this is accomplished by using a10 to enable auto precharge in conjunction with a specific read or write command. a precharge of the bank/row that is addressed with the read or write command is automatically performed upon completion of the read or write burst, except in the continuous page burst mode where auto precharge does not apply. in the specific case of write burst mode set to single location access with burst length set to continuous, the burst length setting is the overriding setting and auto precharge does not apply. auto precharge is nonpersistent in that it is either enabled or disabled for each individual read or write command. auto precharge ensures that the precharge is initiated at the earliest valid stage within a burst. another command cannot be issued to the same bank until the precharge time ( t rp) is completed. this is determined as if an explicit precharge command was is- sued at the earliest possible time, as described for each burst type in the burst type (page 46) section. micron sdram supports concurrent auto precharge; cases of concurrent auto pre- charge for reads and writes are defined below. read with auto precharge interrupted by a read (with or without auto precharge) a read to bank m will interrupt a read on bank n following the programmed cas la- tency. the precharge to bank n begins when the read to bank m is registered (see fig- ure 40 (page 68)). read with auto precharge interrupted by a write (with or without auto precharge) a write to bank m will interrupt a read on bank n when registered. dqm should be used two clocks prior to the write command to prevent bus contention. the pre- charge to bank n begins when the write to bank m is registered (see figure 41 (page 69)). write with auto precharge interrupted by a read (with or without auto precharge) a read to bank m will interrupt a write on bank n when registered, with the data-out appearing cl later. the precharge to bank n will begin after t wr is met, where t wr be- gins when the read to bank m is registered. the last valid write to bank n will be da- ta-in registered one clock prior to the read to bank m (see figure 46 (page 74)). write with auto precharge interrupted by a write (with or without auto precharge) a write to bank m will interrupt a write on bank n when registered. the precharge to bank n will begin after t wr is met, where t wr begins when the write to bank m is reg- 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 67 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. istered. the last valid data write to bank n will be data registered one clock prior to a write to bank m (see figure 47 (page 74)). figure 40: read with auto precharge interrupted by a read dont care clk dq d out t2 t1 t4 t3 t6 t5 t0 command read - ap bank n nop nop nop nop d out d out d out nop t7 bank n cl = 3 (bank m) bank m address idle nop bank n, col a bank m, col d read - ap bank m internal states t page active read with burst of 4 interrupt burst, precharge page active read with burst of 4 precharge rp - bank n t rp - bank m cl = 3 (bank n) note: 1. dqm is low. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 68 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 41: read with auto precharge interrupted by a write clk dq d out t2 t1 t4 t3 t6 t5 t0 command nop nop nop nop d in d in d in d in nop t7 bank n bank m address idle nop dqm 1 bank n, col a bank m, col d write - ap bank m internal states t page active read with burst of 4 interrupt burst, precharge page active write with burst of 4 write-back rp - bank n t wr - bank m cl = 3 (bank n) read - ap bank n dont care transitioning data note: 1. dqm is high at t2 to prevent d out a + 1 from contending with d in d at t4. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 69 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 42: read with auto precharge t ch t cl t ck t ac t lz t rp t ras t rcd cl = 2 t rc cke clk dq a10 t oh d out m t cmh t cms t ah t as t ah t as t ah t as row row bank bank row row bank t hz t oh d out m + 3 t ac t oh t ac t oh t ac d out m + 2 d out m + 1 command t cmh t cms nop nop nop nop active nop read nop active enable auto precharge dont care undefined t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 ba0, ba1 dqm address note: 1. for this example, bl = 4 and cl = 2. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 70 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 43: read without auto precharge t ch t cl t ck t ac t lz t rp t ras t rcd cl = 2 t rc cke clk dq a10 t oh d out t cmh t cms t ah t as t ah t as t ah t as row row bank bank(s) bank row row bank t hz t oh d out t ac t oh t ac t oh t ac d out d out command t cmh t cms precharge nop nop nop active nop read nop active disable auto precharge single bank all banks dont care undefined t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 ba0, ba1 dqm address note: 1. for this example, bl = 4, cl = 2, and the read burst is followed by a manual pre- charge. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 71 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 44: single read with auto precharge t ch t cl t ck t ac t oh t lz t rp t ras t rcd cl = 2 t rc cke clk dq a10 d out t cmh t cms t ah t as t ah t as t ah t as row row bank bank row row bank command t cmh t cms nop nop nop nop active nop read active enable auto precharge dont care undefined t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 ba0, ba1 dqm address note: 1. for this example, bl = 1 and cl = 2. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 72 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 45: single read without auto precharge all banks t ch t cl t ck t ac t lz t rp t ras t rcd cl = 2 t rc cke clk dq a10 t oh d out t cmh t cms t ah t as t ah t as t ah t as row row bank bank(s) bank row row bank t hz command t cmh t cms nop nop nop precharge active nop read active nop disable auto precharge single bank dont care undefined t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 ba0, ba1 dqm address note: 1. for this example, bl = 1, cl = 2, and the read burst is followed by a manual pre- charge. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 73 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 46: write with auto precharge interrupted by a read dont care clk dq t2 t1 t4 t3 t6 t5 t0 command write - ap bank n nop nop nop nop d in d in nop nop t7 bank n bank m address bank n, col a bank m, col d read - ap bank m internal states t page active write with burst of 4 interrupt burst, write-back precharge page active read with burst of 4 t t rp - bank m d out d out cl = 3 (bank m) rp - bank n wr - bank n note: 1. dqm is low. figure 47: write with auto precharge interrupted by a write dont care clk dq t2 t1 t4 t3 t6 t5 t0 command write - ap bank n nop nop nop nop d in d in d in d in d in d in d in nop t7 bank n bank m address nop bank n, col a bank m, col d write - ap bank m internal states t page active write with burst of 4 interrupt burst, write-back precharge page active write with burst of 4 write-back wr - bank n t rp - bank n t wr - bank m note: 1. dqm is low. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 74 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 48: write with auto precharge enable auto precharge t ch t cl t ck t rp t ras t rcd t rc cke clk dq a10 t cmh t cms t ah t as row bank row bank t wr dont care d in t dh t ds d in d in d in command t cmh t cms nop nop nop active nop write nop nop nop row bank row t ah t as t ah t as t dh t ds t dh t ds t dh t ds t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 t9 dqm ba0, ba1 address active note: 1. for this example, bl = 4. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 75 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 49: write without auto precharge disable auto precharge all banks t ch t cl t ck t rp t ras t rcd t rc cke clk dq a10 t cmh t cms t ah t as row bank bank row bank t wr dont care d in t dh t ds d in d in d in command t cmh t cms nop nop nop active nop write precharge nop nop row bank row t ah t as t ah t as t dh t ds t dh t ds t dh t ds single bank t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 t9 dqm ba0, ba1 address active note: 1. for this example, bl = 4 and the write burst is followed by a manual precharge. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 76 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 50: single write with auto precharge enable auto precharge t ch t cl t ck t rp t ras t rcd t rc cke clk dq a10 t cmh t cms t ah t as row bank row bank t wr dont care d in t dh t ds command t cmh t cms nop nop nop active nop write nop nop row bank row t ah t as t ah t as t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 dqm ba0, ba1 address active note: 1. for this example, bl = 1. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 77 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 51: single write without auto precharge t ch t cl t ck t rp t ras t rcd t wr t rc cke clk dq a10 t cmh t cms t ah t as t ah t as t ah t as row bank bank bank row row bank command t cmh t cms nop nop nop precharge active nop write active nop disable auto precharge dont care t ckh t cks column m t0 t1 t2 t4 t3 t5 t6 t7 t8 ba0, ba1 dqm address d in t dh t ds all banks single bank note: 1. for this example, bl = 1 and the write burst is followed by a manual precharge. 256mb: x4, x8, x16 sdram precharge operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 78 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. auto refresh operation the auto refresh command is used during normal operation of the device to refresh the contents of the array. this command is nonpersistent, so it must be issued each time a refresh is required. all active banks must be precharged prior to issuing an auto refresh command. the auto refresh command should not be issued until the minimum t rp is met following the precharge command. addressing is generated by the internal refresh controller. this makes the address bits dont care during an au- to refresh command. after the auto refresh command is initiated, it must not be interrupted by any exe- cutable command until t rfc has been met. during t rfc time, command inhibit or nop commands must be issued on each positive edge of the clock. the sdram re- quires that every row be refreshed each t ref period. providing a distributed auto re- fresh commandcalculated by dividing the refresh period ( t ref) by the number of rows to be refreshedmeets the timing requirement and ensures that each row is re- freshed. alternatively, to satisfy the refresh requirement a burst refresh can be employed after every t ref period by issuing consecutive auto refresh commands for the num- ber of rows to be refreshed at the minimum cycle rate ( t rfc). 256mb: x4, x8, x16 sdram auto refresh operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 79 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 52: auto refresh mode all banks dont care t ch t cl t ck cke clk dq t rfc ( ) ( ) ( ) ( ) t rp ( ) ( ) ( ) ( ) command t cmh t cms nop nop ( ) ( ) ( ) ( ) bank active auto refresh ( ) ( ) ( ) ( ) nop nop precharge precharge all active banks auto refresh t rfc high-z bank(s) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) t ah t as t ckh t cks nop ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) row ( ) ( ) ( ) ( ) single bank a10 row ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) t0 t1 t2 tn + 1 to + 1 ba0, ba1 address dqm ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) note: 1. back-to-back auto refresh commands are not required. 256mb: x4, x8, x16 sdram auto refresh operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 80 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. self refresh operation the self refresh mode can be used to retain data in the device, even when the rest of the system is powered down. when in self refresh mode, the device retains data without ex- ternal clocking. the self refresh command is initiated like an auto refresh com- mand, except cke is disabled (low). after the self refresh command is registered, all the inputs to the device become dont care with the exception of cke, which must remain low. after self refresh mode is engaged, the device provides its own internal clocking, ena- bling it to perform its own auto refresh cycles. the device must remain in self re- fresh mode for a minimum period equal to t ras and remains in self refresh mode for an indefinite period beyond that. the procedure for exiting self refresh requires a sequence of commands. first, clk must be stable prior to cke going back high. (stable clock is defined as a signal cycling within timing constraints specified for the clock ball.) after cke is high, the device must have nop commands issued for a minimum of two clocks for t xsr because time is required for the completion of any internal refresh in progress. upon exiting the self refresh mode, auto refresh commands must be issued accord- ing to the distributed refresh rate ( t ref/refresh row count) as both self refresh and auto refresh utilize the row refresh counter. 256mb: x4, x8, x16 sdram self refresh operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 81 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 53: self refresh mode all banks t ch t cl t ck t rp cke clk dq enter self refresh mode precharge all active banks t xsr clk stable prior to exiting self refresh mode exit self refresh mode (restart refresh time base) ( ) ( ) ( ) ( ) ( ) ( ) dont care command t cmh t cms auto refresh precharge nop nop bank(s) high-z t cks t ah t as auto refresh t ckh t cks a10 t0 t1 t2 tn + 1 to + 1 to + 2 ba0, ba1 dqm address ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) single bank note: 1. each auto refresh command performs a refresh cycle. back-to-back commands are not required. 256mb: x4, x8, x16 sdram self refresh operation pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 82 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. power-down power-down occurs if cke is registered low coincident with a nop or command in- hibit when no accesses are in progress. if power-down occurs when all banks are idle, this mode is referred to as precharge power-down; if power-down occurs when there is a row active in any bank, this mode is referred to as active power-down. entering power- down deactivates the input and output buffers, excluding cke, for maximum power savings while in standby. the device cannot remain in the power-down state longer than the refresh period (64ms) because no refresh operations are performed in this mode. the power-down state is exited by registering a nop or command inhibit with cke high at the desired clock edge (meeting t cks). figure 54: power-down mode all banks t ch t cl t ck two clock cycles cke clk dq all banks idle, enter power-down mode precharge all active banks input buffers gated off while in power-down mode exit power-down mode ( ) ( ) dont care t cks t cks command t cmh t cms precharge nop nop active nop ( ) ( ) ( ) ( ) all banks idle ba0, ba1 bank bank(s) ( ) ( ) ( ) ( ) high-z t ah t as t ckh t cks dqm ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) address row ( ) ( ) ( ) ( ) single bank a10 row ( ) ( ) ( ) ( ) t0 t1 t2 tn + 1 tn + 2 ( ) ( ) note: 1. violating refresh requirements during power-down may result in a loss of data. 256mb: x4, x8, x16 sdram power-down pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 83 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. clock suspend the clock suspend mode occurs when a column access/burst is in progress and cke is registered low. in the clock suspend mode, the internal clock is deactivated, freezing the synchronous logic. for each positive clock edge on which cke is sampled low, the next internal positive clock edge is suspended. any command or data present on the input balls when an in- ternal clock edge is suspended will be ignored; any data present on the dq balls re- mains driven; and burst counters are not incremented, as long as the clock is suspen- ded. exit clock suspend mode by registering cke high; the internal clock and related opera- tion will resume on the subsequent positive clock edge. figure 55: clock suspend during write burst dont care d in command address write bank, col n d in nop nop clk t2 t1 t4 t3 t5 t0 cke internal clock nop d in d in note: 1. for this example, bl = 4 or greater, and dqm is low. 256mb: x4, x8, x16 sdram clock suspend pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 84 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 56: clock suspend during read burst dont care clk dq d out t2 t1 t4 t3 t6 t5 t0 command address read nop nop nop bank, col n nop d out d out d out cke internal clock nop note: 1. for this example, cl = 2, bl = 4 or greater, and dqm is low. 256mb: x4, x8, x16 sdram clock suspend pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 85 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. figure 57: clock suspend mode t ch t cl t ck t ac t lz dqm clk dq a10 t oh d out t ah t as t ah t as t ah t as bank t dh d in t ac t hz d out command t cmh t cms nop nop nop nop nop read write dont care undefined cke t cks t ckh bank column m t ds d in nop t ckh t cks t cmh t cms column e t0 t1 t2 t3 t4 t5 t6 t7 t8 t9 ba0, ba1 address note: 1. for this example, bl = 2, cl = 3, and auto precharge is disabled. 8000 s. federal way, p.o. box 6, boise, id 83707-0006, tel: 208-368-3900 www.micron.com/productsupport customer comment line: 800-932-4992 micron and the micron logo are trademarks of micron technology, inc. all other trademarks are the property of their respective owners. this data sheet contains minimum and maximum limits specified over the power supply and temperature range set forth herein. although considered final, these specifications are subject to change, as further product development and data characterization some- times occur. 256mb: x4, x8, x16 sdram clock suspend pdf: 09005aef8091e6d1 256mb_sdr.pdf - rev. u 05/13 en 86 micron technology, inc. reserves the right to change products or specifications without notice. ? 1999 micron technology, inc. all rights reserved. |
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