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1 2015 integrated device technology, inc. all rights reserved. product specifications subject to change without notice. dsc-4662/7 ? march 2015 3.3 volt cmos syncfifo tm with bus-matching 256 x 36 1,024 x 36 idt72v3623 idt72v3643 idt and the idt logo are registered trademark of integrated device technology, inc. syncfifo is a trademark of integrated dev ice technology, inc. commercial temperature range features: ? ? ? ? ? memory storage capacity: idt72v3623?256 x 36 idt72v3643?1,024 x 36 ? ? ? ? ? clock frequencies up to 100 mhz (6.5 ns access time) ? ? ? ? ? clocked fifo buffering data from port a to port b ? ? ? ? ? idt standard timing (using ef and ff ) or first word fall through timing (using or and ir flag functions) ? ? ? ? ? programmable almost-empty and almost-full flags; each has three default offsets (8, 16 and 64) ? ? ? ? ? serial or parallel programming of partial flags ? ? ? ? ? port b bus sizing of 36 bits (long word), 18 bits (word) and 9 bits (byte) ? ? ? ? ? big- or little-endian format for word and byte bus sizes ? ? ? ? ? reset clears data and configures fifo, partial reset clears data but retains configuration settings ? ? ? ? ? mailbox bypass registers for each fifo ? ? ? ? ? free-running clka and clkb may be asynchronous or coincident (simultaneous reading and writing of data on a single clock edge is permitted) ? ? ? ? ? easily expandable in width and depth ? ? ? ? ? auto power down minimizes power dissipation ? ? ? ? ? available in a space-saving 128-pin thin quad flatpack (tqfp) ? ? ? ? ? pin and functionally compatible versions of the 5v operating idt723623/723643 ? ? ? ? ? industrial temperature range (?40 c to +85 c) is available ? ? ? ? ? green parts available, see ordering information functional block diagram mail 1 register programmable flag offset registers status flag logic ef /or ae 36 ff /ir af 36 timing mode fwft a 0 -a 35 spm fs0/sd fs1/ sen b 0 -b 35 write pointer read pointer mail 2 register mbf2 clkb csb w /rb enb mbb be bm size port-b control logic 10 4662 drw01 input register ram array 256 x 36 1,024 x 36 clka csa w/ r a ena mba port-a control logic fifo1 mail1, mail2, reset logic rs1 mbf1 36 bus- matching output register prs 36 36 rs2 36
2 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range read access times as fast as 6.5 ns. the 256/1,024 x 36 dual-port sram fifo buffers data from port a to port b. fifo data on port b can output in 36-bit, 18-bit, or 9-bit formats with a choice of big- or little-endian configurations. these devices are synchronous (clocked) fifos, meaning each port employs a synchronous interface. all data transfers through a port are gated description: the idt72v3623/72v3643 are pin and functionally compatible versions of the idt723623/723643, designed to run off a 3.3v supply for exceptionally low power consumption. these devices are monolithic, high-speed, low-power, cmos unidirectional synchronous (clocked) fifo memory which supports clock frequencies up to 100 mhz and has pin configuration tqfp (pk128, order code: pf) top view w/ r a clkb 4662 drw02 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 ena clka gnd a35 a34 a33 a32 vcc a31 a30 gnd a29 a28 a27 a26 a25 a24 a23 be/ fwft gnd a22 v cc a21 a20 a19 a18 gnd a17 a16 a15 a14 a13 v cc a12 gnd a11 a10 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 102 101 128 127 126 125 124 123 122 121 120 119 118 117 116 115 114 113 112 111 110 109 108 107 106 105 v cc v cc b35 b34 b33 b32 gnd gnd b31 b30 b29 b28 b27 b26 v cc b25 b24 bm gnd b23 b22 b21 b20 b19 b18 gnd b17 b16 v cc b15 b14 b13 b12 gnd b11 b10 csa ff /ir nc prs v cc af nc mbf2 mba rs1 fs0/sd gnd gnd fs1/ sen rs2 mbb mbf1 v cc ae nc ef /or nc gnd csb w /rb enb a9 a8 a7 a6 gnd a5 a4 a3 spm v cc a2 a1 a0 gnd b0 b1 b2 b3 b4 b5 gnd b6 v cc b7 b8 b9 104 103 index size note: 1. nc ? no internal connection
3 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 to the low-to-high transition of a port clock by enable signals. the clocks for each port are independent of one another and can be asynchronous or coincident. the enables for each port are arranged to provide a simple bidirectional interface between microprocessors and/or buses with synchronous control. communication between each port may bypass the fifo via two mailbox registers. the mailbox registers' width matches the selected port b bus width. each mailbox register has a flag ( mbf1 and mbf2 ) to signal when new mail has been stored. two kinds of reset are available on these fifos: reset and partial reset. reset initializes the read and write pointers to the first location of the memory array and selects serial flag programming, parallel flag programming, or one of three possible default flag offset settings, 8, 16 or 64. partial reset also sets the read and write pointers to the first location of the memory. unlike reset, any settings existing prior to partial reset (i.e., programming method and partial flag default offsets) are retained. partial reset is useful since it permits flushing of the fifo memory without changing any configuration settings. these devices have two modes of operation: in the idt standard mode , the first word written to an empty fifo is deposited into the memory array. a read operation is required to access that word (along with all other words residing in memory). in the first word fall through mode (fwft), the first word written to an empty fifo appears automatically on the outputs, no read operation required (nevertheless, accessing subsequent words does neces- sitate a formal read request). the state of the be/ fwft pin during reset determines the mode in use. the fifo has a combined empty/output ready flag ( ef /or ) and a combined full/input ready flag ( ff /ir). the ef and ff functions are selected in the idt standard mode. ef indicates whether or not the fifo memory is empty. ff shows whether the memory is full or not. the ir and or functions are selected in the first word fall through mode. ir indicates whether or not the fifo has available memory locations. or shows whether the fifo has data available for reading or not. it marks the presence of valid data on the outputs. the fifo has a programmable almost-empty flag ( ae ) and a programmable almost-full flag ( af ). ae indicates when a selected number of words remain in the fifo memory. af indicates when the fifo contains more than a selected number of words. ff /ir and af are two-stage synchronized to the port clock that writes data into its array. ef /or and ae are two-stage synchronized to the port clock that reads data from its array. programmable offsets for ae and af are loaded in parallel using port a or in serial via the sd input. the serial programming mode pin ( spm ) makes this selection. three default offset settings are also provided. the ae threshold can be set at 8, 16 or 64 locations from the empty boundary and the af threshold can be set at 8, 16 or 64 locations from the full boundary. all these choices are made using the fs0 and fs1 inputs during reset. two or more devices may be used in parallel to create wider data paths. in first word fall through mode, more than one device may be connected in series to create greater word depths. the addition of external components is unnecessary. if, at any time, the fifo is not actively performing a function, the chip will automatically power down. during the power down state, supply current consumption (i cc ) is at a minimum. initiating any operation (by activating control inputs) will immediately take the device out of the power down state. the idt72v3623/72v3643 are characterized for operation from 0 c to 70 c. industrial temperature range (-40 c to +85 c) is available by special order. they are fabricated using high speed, submicron cmos technology.
4 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range symbol name i/o description a0-a35 port a data i/o 36-bit bidirectional data port for side a. ae almost-empty flag o programmable almost-empty flag synchronized to clkb. it is low when the number of (port b) words in the fifo is less than or equal to the value in the almost-empty b offset register, x. af almost-full flag o programmable almost-full flag synchronized to clka. it is low when the number of empty (port a) locations in the fifo is less than or equal to the value in the almost-full a offset register, y. b0-b35 port b data i/o 36-bit bidirectional data port for side b. be/ fwft big-endian/ i this is a dual purpose pin. during master reset, a high on be will select big-endian first word operation. in this case, depending on the bus size, the most significant byte or word written to fall through port a is read from port b first. a low on be will select little-endian operation. in this case, the least significant byte or word written to port a is read from port b first. after master reset, this pin selects the timing mode. a high on fwft selects idt standard mode, a low selects first word fall through mode. once the timing mode has been selected, the level on fwft must be static throughout device operation. bm bus-match select i a high on this pin enables either byte or word bus width on port b, depending on the state of (port b) size. a low selects long word operation. bm works with size and be to select the bus size and endian arrangement for port b. the level of bm must be static throughout device operation. clka port a clock i clka is a continuous clock that synchronizes all data transfers through port a and can be asynchronous or coincident to clkb. ff /ir and af are synchronized to the low-to-high transition of clka. clkb port b clock i clkb is a continuous clock that synchronizes all data transfers through port b and can be asynchronous or coincident to clka. ef /or and ae are synchronized to the low-to-high transition of clkb. csa port a chip i csa must be low to enable to low-to-high transition of clka to read or write on port a. select the a0-a35 outputs are in the high-impedance state when csa is high. csb port b chip i csb must be low to enable a low-to-high transition of clkb to read or write data on select port b. the b0-b35 outputs are in the high-impedance state when csb is high. ef /or empty/output o this is a dual function pin. in the idt standard mode, the ef function is selected. ef indicates ready flag whether or not the fifo memory is empty. in the fwft mode, the or function is selected. (port b) or indicates the presence of valid data on the b0-b35 outputs, available for reading. ef /or is synchronized to the low-to-high transition of clkb. ena port a enable i ena must be high to enable a low-to-high tr ansition of clka to read or write data on port a. enb port b enable i enb must be high to enable a low-to-h igh transition of clkb to read or write data on port b. ff /ir full/input o this is a dual function pin. in the idt standard m ode, the ff function is selected. ff indicates ready flag whether or not the fifo memory is full. in the fwft mode, the ir function is selected. ir (port a) indicates whether or not there is space available for writing to the fifo memory. ff /ir is synchronized to the low-to-high transition of clka. fs1/ sen flag offset i fs1/ sen and fs0/sd are dual-purpose inputs used for flag offset register programming. select 1/ during reset, fs1/ sen and fs0/sd, together with spm , select the flag offset programming serial enable method. three offset register programming methods are available: automatically load one of three preset values (8, 16, or 64), parallel load from port a, and serial load. fs0/sd flag offset i when serial load is selected for flag offset register programming, fs1/ sen is used as an serial data enable synchronous to the low-to-high transition of clka. when fs1/ sen is low, a rising edge on clka load the bit present on fs0/sd into the x and y registers. the number of bit writes required to program the offset registers is 16 for the idt72v3623 and 20 for the idt72v3643. the first bit write stores the y-register msb and the last bit write stores the x-register lsb. pin descriptions
5 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 symbol name i/o description pin descriptions (continued) mba port a mailbox i a high level on mba chooses a mailbox register for a port a read or write operation. select mbb port b mailbox i a high level on mbb chooses a mailbox register for a port b read or write operation. select when the b0-b35 outputs are active, a high level on mbb selects data from the mail1 register for output and a low level selects fifo data for output. mbf1 mail1 register flag o mbf1 is set low by a low-to-high transition of clka that writes data to the mail1 register. writes to the mail1 register are inhibited while mbf1 is low. mbf1 is set high by a low-to-high transition of clkb when a port b read is selected and mbb is high. mbf1 is set high following either a reset ( rs1 ) or partial reset ( prs ). mbf2 mail2 register flag o mbf2 is set low by a low-to-high transition of clkb that writes data to the mail2 register. writes to the mail2 register are inhibited while mbf2 is low. mbf2 is set high by a low- to-high transition of clka when a port a read is selected and mba is high. mbf2 is set high following either a reset ( rs2 ) or partial reset ( prs ). rs1 , rs2 resets i a low on both pins initializes the fifo read and write pointers to the first location of memory and sets the port b output register to all zeroes. a low-to-high transition on rs1 selects the programming method (serial or parallel) and one of three programmable flag default offsets. it also configures port b for bus size and endian arrangement. four low-to-high transitions of clka and four low-to-high transitions of clkb must occur while rs1 is low. prs partial reset i a low on this pin initializes the fifo read and write pointers to the first location of memory and sets the port b output register to all zeroes. during partial reset, the currently selected bus size, endian arrangement, programming method (serial or parallel), and programmable flag settings are all retained. size bus size select i a high on this pin when bm is high selects byte bus (9-bit) size on port b. a low on this pin (port b) when bm is high selects word (18-bit) bus size. size works with bm and be to select the bus size and endian arrangement for port b. the level of size must be static throughout device operation. spm serial programming i a low on this pin selects serial programming of partial flag offsets. a high on this pin selects mode parallel programming or default offsets (8, 16, or 64). w/ r a port a write/ i a high selects a write operation and a low selects a read operation on port a for a low-to-high read select transition of clka. the a0-a35 outputs are in the high impedance state when w/ r a is high. w /rb port b write/ i a low selects a write operation and a high selects a read operation on port b for a low-to-high read select transition of clkb. the b0-b35 outputs are in the high impedance state when w /rb is low.
6 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range absolute maximum ratings over operating free-air temperature range (unless otherwise noted) (1) symbol rating commercial unit v cc supply voltage range ?0.5 to +4.6 v v i ( 2) input voltage range ?0.5 to v cc +0.5 v v o (2) output voltage range ?0.5 to v cc +0.5 v i ik input clamp current (v i < 0 or v i > v cc ) 20 ma i ok output clamp current (v o = < 0 or v o > v cc ) 50 ma i out continuous output current (v o = 0 to v cc ) 50 ma i cc continuous current through v cc or gnd 400 ma t stg storage temperature range ?65 to 150 c notes: 1. stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. these are stress rat ings only and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. exposure to absolute-m aximum-rated conditions for extended periods may affect device reliability. 2. the input and output voltage ratings may be exceeded provided the input and output current ratings are observed. notes: 1. for 10ns speed grade only: vcc = 3.3v +/-0.15v; t a = 0 to +70 c; jedec jesd8-a compliant. 2. all typical values are at v cc = 3.3v, t a = 25 c. 3. for additional i cc information, see figure 1, typical characteristics: supply current (i cc ) vs. clock frequency (f s ) . 4. characterized values, not currently tested. 5. industrial temperature range is available by special order. electrical characteristics over recommended operating free-air temperature range (unless otherwise noted) idt72v3623 idt72v3643 commercial t clk = 10 (1) , 15ns symbol parameter test conditions min. typ. (2) max. unit v oh output logic "1" voltage v cc = 3.0v, i oh = ?4 ma 2.4 ? ? v v ol output logic "0" voltage v cc = 3.0v, i ol = 8 ma ? ? 0.5 v i li input leakage current (any input) v cc = 3.6v, v i = v cc or 0 ? ? 10 a i lo output leakage current v cc = 3.6v, v o = v cc or 0 ? ? 10 a i cc2 (3) standby current (with clka and clkb running) v cc = 3.6v, v i = v cc - 0.2v or 0 ? ? 5 ma i cc3 (3) standby current (no clocks running) v cc = 3.6v, v i = v cc - 0.2v or 0 ? ? 1 ma c in (4) input capacitance v i = 0, f = 1 mhz ? 4 ? pf c out (4) output capacitance v o = 0, f = 1 mhz ? 8 ? pf note: 1. for 10ns (100 mhz operation), v cc = 3.3v +/-0.15v;t a = 0 to +70 c; jedec jesd8-a compliant. symbol parameter min. typ. max. unit v cc (1) supply voltage 3.0 3.3 3.6 v v ih high-level input voltage 2 ? v cc +0.5 v v il low-level input voltage ? ? 0.8 v i oh high-level output current ? ? ?4 ma i ol low-level output current ? ? 8 ma t a operating temperature 0 ? 70 c recommended operating conditions
7 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 determining active current consumption and power dissipation the i cc(f) current for the graph in figure 1 was taken while simultaneously reading and writing a fifo on the idt72v3623/72v3643 with clka and clkb set to f s . all data inputs and data outputs change state during each clock cycle to consume the highest supply current. data outputs w ere disconnected to normalize the graph to a zero capacitance load. once the capacitance load per data-output channel and the numb er of idt72v3623/72v3643 inputs driven by ttl high levels are known, the power dissipation can be calculated with the equation below. calculating power dissipation with i cc(f) taken from figure 1, the maximum power dissipation (pt) of these fifos may be calculated by: p t = v cc x i cc (f) + (c l x v cc 2 x f o ) n where: n = number of used outputs (36-bit (long word), 18-bit (word) or 9-bit (byte) bus size) c l = output capacitance load f o = switching frequency of an output figure 1. typical characteristics: supply current (i cc ) vs. clock frequency (f s ) 010203040506070 0 25 50 75 100 125 150 v cc = 3.3v f s clock frequency mhz i cc(f) supply current ma f data = 1/2 f s t a = 25 c c l = 0 pf v cc = 3.0v v cc = 3.6v 4662 drw 03 175 200 80 90 100
8 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range idt72v3623l10 (1) idt72v3623l15 idt72v3643l10 (1) idt72v3643l15 symbol parameter min. max. min. max. unit f s clock frequency, clka or clkb ? 100 ? 66.7 mhz t clk clock cycle time, clka or clkb 10 ? 15 ? ns t clkh pulse duration, clka or clkb high 4.5 ? 6 ? ns t clkl pulse duration, clka and clkb low 4.5 ? 6 ? ns t ds setup time, a0-a35 before clka and b0-b35 before clkb 3?4?ns t ens1 setup time, csa , before clka ; csb , before clkb 4 ? 4.5 ? ns t ens2 setup time, ena, w/ r a and mba before clka ; enb, w /rb and mbb 3 ? 4.5 ? ns before clkb t rsts setup time, rs1 or prs low before clka or clkb (2) 5?5?ns t fss setup time, fs0 and fs1 before rs1 high 7.5 ? 7.5 ? ns t bes setup time, be/ fwft before rs1 high 7.5 ? 7.5 ? ns t spms setup time, spm before rs1 high 7.5 ? 7.5 ? ns t sds setup time, fs0/sd before clka 3?4?ns t sens setup time, fs1/ sen before clka 3?4?ns t fws setup time, fwft before clka 0?0?ns t dh hold time, a0-a35 after clka and b0-b35 after clkb 0.5 ? 1 ? ns t enh hold time, csa , w/ r a, ena, and mba after clka ; csb , w /rb, enb, and 0.5 ? 1 ? ns mbb after clkb t rsth hold time, rs1 or prs low after clka or clkb (2) 4? 4?ns t fsh hold time, fs0 and fs1 after rs1 high 2 ? 2 ? ns t beh hold time, be/ fwft after rs1 high 2 ? 2 ? ns t spmh hold time, spm after rs1 high 2 ? 2 ? ns t sdh hold time, fs0/sd after clka 0.5 ? 1 ? ns t senh hold time, fs1/ sen high after clka 0.5 ? 1 ? ns t sph hold time, fs1/ sen high after rs1 high 2 ? 2 ? ns t skew1 (3) skew time between clka and clkb for ef /or and ff /ir 7.5 ? 7.5 ? ns t skew2 (3,4) skew time between clka and clkb for ae and af 12 ? 12 ? ns notes: 1. for 10ns speed grade only: vcc = 3.3v +/-0.15v, t a = 0 to +70 c; jedec jesd8-a compliant. 2. requirement to count the clock edge as one of at least four needed to reset a fifo. 3. skew time is not a timing constraint for proper device operation and is only included to illustrate the timing relationship b etween clka cycle and clkb cycle. 4. design simulated, not tested. 5. industrial temperature range is available by special order. timing requirements over recommended ranges of supply voltage and operating free-air temperature commercial: vcc=3.3v 0.30v; for 10ns (100 mhz) operation, vcc=3.3v 0.15v; ta = 0 c to +70 c; jedec jesd8-a compliant
9 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 idt72v3623l10 (1) idt72v3623l15 idt72v3643l10 (1) idt72v3643l15 symbol parameter min. max. min. max. unit t a access time, clka to a0-a35 and clkb to b0-b35 2 6.5 2 10 ns t wff propagation delay time, clka to ff /ir 2 6.5 2 8 ns t ref propagation delay time, clkb to ef /or 1 6.5 1 8 ns t pae propagation delay time, clkb to ae 1 6.5 1 8 ns t paf propagation delay time, clka to af 1 6.5 1 8 ns t pmf propagation delay time, clka to mbf1 low or mbf2 and clkb to mbf2 low 0 6.5 0 8 ns or mbf1 high t pmr propagation delay time, clka to b0-b35 (2) and clkb to a0-a35 (3) 28 210ns t mdv propagation delay time, mba to a0-a35 valid and mbb to b0-b35 valid 2 6.5 2 10 ns t rsf propagation delay time, rs1 or prs low to ae low, af high, mbf1 high 1 10 1 15 ns and mbf2 high t en enable time, csa and w/ r a low to a0-a35 active and csb low and w /rb 2 6 2 10 ns high to b0-b35 active t dis disable time, csa or w/ r a high to a0-a35 at high impedance and csb high 1 6 1 8 ns or w /rb low to b0-b35 at high impedance notes: 1. for 10ns speed grade only: vcc = 3.3v +/-0.15v, t a = 0 to +70 c; jedec jesd8-a compliant. 2. writing data to the mail1 register when the b0-b35 outputs are active and mbb is high. 3. writing data to the mail2 register when the a0-a35 outputs are active and mba is high. 4. industrial temperature range is available by special order. switching characteristics over recommended ranges of supply voltage and operating free-air temperature, c l = 30 pf commercial: vcc=3.3v 0.30v; for 10ns (100 mhz) operation, vcc=3.3v 0.15v; ta = 0 c to +70 c; jedec jesd8-a compliant
10 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range a high on the be/ fwft input when the reset ( rs1 ) input goes from low to high will select a big-endian arrangement. in this case, the most significant byte (word) of the long word written to port a will be read from port b first; the least significant byte (word) of the long word written to port a will be read from port b last. a low on the be/ fwft input when the reset ( rs1 ) input goes from low to high will select a little-endian arrangement. in this case, the least significant byte (word) of the long word written to port a will be read from port b first; the most significant byte (word) of the long word written to port a will be read from port b last. refer to figure 2 for an illustration of the be function. see figure 3 (reset) for an endian select timing diagram. ? timing mode selection after reset, the fwft select function is active, permitting a choice between two possible timing modes: idt standard mode or first word fall through (fwft) mode. once the reset ( rs1 ) input is high, a high on the be/ fwft input during the next low-to-high transition of clka and clkb will select idt standard mode. this mode uses the empty flag function ( ef ) to indicate whether or not there are any words present in the fifo memory. it uses the full flag function ( ff ) to indicate whether or not the fifo memory has any free space for writing. in idt standard mode, every word read from the fifo, including the first, must be requested using a formal read operation. once the reset ( rs1 ) input is high, a low on the be/ fwft input during the next low-to-high transition of clka and clkb will select fwft mode. this mode uses the output ready function (or) to indicate whether or not there is valid data at the data outputs (b0-b35). it also uses the input ready function (ir) to indicate whether or not the fifo memory has any free space for writing. in the fwft mode, the first word written to an empty fifo goes directly to data outputs, no read request necessary. subsequent words must be accessed by performing a formal read operation. following reset, the level applied to the be/ fwft input to choose the desired timing mode must remain static throughout fifo operation. refer to figure 3 (reset) for a first word fall through select timing diagram. programming the almost-empty and almost-full flags two registers in the idt72v3623/72v3643 are used to hold the offset values for the almost-empty and almost-full flags. the almost- empty flag ( ae ) offset register is labeled x and almost-full flag ( af ) offset register is labeled y. the offset registers can be loaded with preset values during the reset of the fifo, programmed in parallel using the fifo?s port a data inputs, or programmed in serial using the serial data (sd) input (see table 1). spm , fs0/sd, and fs1/ sen function the same way in both idt standard and fwft modes. ? preset values to load a fifo?s almost-empty flag and almost-full flag offset registers with one of the three preset values listed in table 1, the serial program mode ( spm ) and at least one of the flag-select inputs must be high during the low- to-high transition of the reset input ( rs1 ). for example, to load the preset value of 64 into x and y, spm , fs0 and fs1 must be high when rs1 returns high. for the relevant preset value loading timing diagram, see figure 3. signal description reset ( rs1 , rs2 ) after power up, a reset operation must be performed by providing a low pulse to rs1 and rs2 simultaneously. afterwards, the fifo memory of the idt72v3623/72v3643 undergoes a complete reset by taking its reset ( rs1 and rs2 ) input low for at least four port a clock (clka) and four port b clock (clkb) low-to-high transitions. the reset inputs can switch asynchronously to the clocks. a reset initializes the internal read and write pointers and forces the full/input ready flag ( ff /ir) low, the empty/output ready flag ( ef /or) low, the almost-empty flag ( ae ) low, and the almost-full flag ( af ) high. a reset ( rs1 ) also forces the mailbox flag ( mbf1 ) of the parallel mailbox register high, and at the same time the rs2 and mbf2 operate likewise. after a reset, the fifo?s full/input ready flag is set high after two write clock cycles to begin normal operation. a low-to-high transition on the flfo reset ( rs1 ) input latches the value of the big-endian (be) input for determining the order by which bytes are transferred through port b. a low-to-high transition on the flfo reset ( rs1 ) input also latches the values of the flag select (fs0, fs1) and serial programming mode ( spm ) inputs for choosing the almost-full and almost-empty offset programming method ( for details see table 1, flag programming, and almost-empty and almost-full flag offset programming section). the relevant reset timing diagram can be found in figure 3. partial reset ( prs ) the fifo memory of the idt72v3623/72v3643 undergoes a limited reset by taking its partial reset ( prs ) input low for at least four port a clock (clka) and four port b clock (clkb) low-to-high transitions. the partial reset input can switch asynchronously to the clocks. a partial reset initializes the internal read and write pointers and forces the full/ input ready flag ( ff /ir) low, the empty/output ready flag ( ef /or) low, the almost-empty flag ( ae ) low, and the almost-full flag ( af ) high. a partial reset also forces the mailbox flag ( mbf1 , mbf2 ) of the parallel mailbox register high. after a partial reset, the fifo?s full/input ready flag is set high after two write clock cycles to begin normal operation. see figure 4, partial reset (idt standard and fwft modes) for the relevant timing diagram. whatever flag offsets, programming method (parallel or serial), and timing mode (fwft or idt standard mode) are currently selected at the time a partial reset is initiated, those settings will be remain unchanged upon completion of the reset operation. a partial reset may be useful in the case where reprogramming a fifo following a reset would be inconvenient. big-endian/first word fall through (be/ fwft ) ? endian selection this is a dual purpose pin. at the time of reset, the be select function is active, permitting a choice of big- or little-endian byte arrangement for data read from port b. this selection determines the order by which bytes (or words) of data are transferred through this port. for the following illustrations, assume that a byte (or word) bus size has been selected for port b. (note that when port b is configured for a long word size, the big- endian function has no application and the be input is a ?don?t care? 1 .) note: 1. either a high or low can be applied to a ?don?t care? input with no change to the logical operation of the fifo. neverthel ess, inputs that are temporarily ?don?t care? (along with unused inputs) must not be left open, rather they must be either high or low.
11 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 table 1 ? flag programming spm fs1/ sen fs0/sd rs1 x and y reglsters (1) hh h 64 hh l 16 hl h 8 hl l parallel programming via port a lh l serial programming via sd lh h reserved ll h reserved ll l reserved note: 1. x register holds the offset for ae ; y register holds the offset for af . ? parallel load from port a to program the x and y registers from port a, perform a reset on with spm high and fs0 and fs1 low during the low-to-high transition of rs1 . after this reset is complete, the first two writes to the fifo do not store data in ram. the first two write cycles load the offset registers in the order y, x. on the third write cycle the fifo is ready to be loaded with a data word. see figure 5, parallel programming of the almost-full flag and almost-empty flag offset values after reset (idt standard and fwft modes), for a detailed timing diagram. the port a data inputs used by the offset registers are (a7-a0), (a8-a0), or (a9-a0) for the idt72v3623 or idt72v3643, respectively. the highest numbered input is used as the most significant bit of the binary number in each case. valid programming values for the registers range from 1 to 252 for the idt72v3623; and 1 to 1,020 for the idt72v3643. after all the offset registers are programmed from port a, the fifo begins normal opera- tion. ? serial load to program the x and y registers serially, initiate a reset with spm low, fs0/sd low and fs1/ sen high during the low-to-high transition of rs1 . after this reset is complete, the x and y register values are loaded bit-wise through the fs0/sd input on each low-to-high transition of clka that the fs1/ sen input is low. there are 16-, 18- or 20-bit writes needed to complete the programming for the idt72v3623 or the idt72v3643, respectively. the two registers are written in the order y, x. each register value can be programmed from 1 to 252 (idt72v3623) or 1 to 1,020 (idt72v3643). when the option to program the offset registers serially is chosen, the full/ input ready ( ff /ir) flag remains low until all register bits are written. ff /ir is set high by the low-to-high transition of clka after the last bit is loaded to allow normal fifo operation. see figure 6, serial programming of the almost-full flag and almost- empty flag offset values after reset (idt standard and fwft modes). fifo write/read operation the state of the port a data (a0-a35) lines is controlled by port a chip select ( csa ) and port a write/read select (w/ r a). the a0-a35 lines are in the high-impedance state when either csa or w/ r a is high. the a0-a35 lines are active outputs when both csa and w/ r a are low. data is loaded into the fifo from the a0-a35 inputs on a low-to-high transition of clka when csa is low, w/ r a is high, ena is high, mba is low, and ff /ir is high (see table 2). fifo writes on port a are independent of any concurrent reads on port b. the port b control signals are identical to those of port a with the exception that the port b write/read select ( w /rb) is the inverse of the port a write/read select (w/ r a). the state of the port b data (b0-b35) lines is controlled by the port b chip select ( csb ) and port b write/read select ( w /rb). the b0-b35 lines are in the high-impedance state when either csb is high or w /rb is low. the b0-b35 lines are active outputs when csb is low and w /rb is high. data is read from the fifo to the b0-b35 outputs by a low-to-high transition of clkb when csb is low, w /rb is high, enb is high, mbb is low, and ef /or is high (see table 3). fifo reads on port b are independent of any concurrent writes on port a. the setup and hold time constraints to the port clocks for the port chip selects and write/read selects are only for enabling write and read operations and are not related to high-impedance control of the data outputs. if a port enable is low during a clock cycle, the port?s chip select and write/read select may change states during the setup and hold time window of the cycle. when operating the fifo in fwft mode and the output ready flag is low, the next word written is automatically sent to the fifo?s output register by the low-to-high transition of the port clock that sets the output ready flag high. when the output ready flag is high, data residing in the fifo?s memory array is clocked to the output register only when a read is selected using the port?s chip select, write/read select, enable, and mailbox select. when operating the fifo in idt standard mode, regardless of whether the empty flag is low or high, data residing in the fifo?s memory array is clocked to the output register only when a read is selected using the port?s chip select, write/read select, enable, and mailbox select. port a write timing diagram can be found in figure 7. relevant port b read timing diagrams together with bus-matching and endian select can be found in figure 8, 9 and 10. synchronized fifo flags each fifo is synchronized to its port clock through at least two flip- flop stages. this is done to improve flag-signal reliability by reducing the probability of metastable events when clka and clkb operate asyn- chronously to one another. ff /ir, and af are synchronized to clka. ef / or and ae are synchronized to clkb. table 4 shows the relationship of each port flag to the number of words stored in memory.
12 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range empty/output ready flags ( ef /or) these are dual purpose flags. in the fwft mode, the output ready (or) function is selected. when the output-ready flag is high, new data is present in the fifo output register. when the output ready flag is low, the previous data word is present in the fifo output register and attempted fifo reads are ignored. in the idt standard mode, the empty flag ( ef ) function is selected. when the empty flag is high, data is available in the fifo?s memory for reading to the output register. when the empty flag is low, the previous data word is present in the fifo output register and attempted fifo reads are ignored. the empty/output ready flag of a fifo is synchronized to the port clock that reads data from its array (clkb). for both the fwft and idt standard modes, the fifo read pointer is incremented each time a new word is clocked to its output register. the state machine that controls an output ready flag monitors a write pointer and read pointer comparator that indicates when the fifo memory status is empty, empty+1, or empty+2. in fwft mode, from the time a word is written to a fifo, it can be shifted to the fifo output register in a minimum of three cycles of the output ready flag synchronizing clock. therefore, an output ready flag is low if a word in memory is the next data to be sent to the flfo output register and csb w /rb enb mbb clkb data b (b0-b35) i/o port functions h x x x x high-impedance none l l l x x input none llh l input none llh h input mail2 write l h l l x output none lhh l output fifo read l h l h x output none lhh h output mail1 read (set mbf1 high) table 3 ? port-b enable function table csa w/ r a ena mba clka data a (a0-a35) i/o port functions h x x x x high-impedance none l h l x x input none lh h l input fifo write lh h h input mail1 write l l l l x output none ll h l output none l l l h x output none ll h h output mail2 read (set mbf2 high) table 2 ? port-a enable function table table 4 ? fifo flag operation (idt standard and fwft modes) synchronized synchronized number of words in fifo (1,2) to clkb to clka idt72v3623 (3) idt72v3643 (3) ef /or ae af ff /ir 00llhh 1 to x 1 to x h l h h (x+1) to [256-(y+1)] (x+1) to [1,024-(y+1)] h h h h (256-y) to 255 (1,024-y) to 1,023 h h l h 256 1,024 h h l l notes: 1. when a word loaded to an empty fifo is shifted to the output register, its previous fifo memory location is free. 2. data in the output register does not count as a "word in fifo memory". since in fwft mode, the first word written to an empt y fifo goes unrequested to the output register (no read operation necessary), it is not included in the memory count. 3. x is the almost-empty offset used by ae . y is the almost-full offset used by af . both x and y are selected during a fifo reset or port a programming.
13 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 three cycles of the port clock that reads data from the fifo have not elapsed since the time the word was written. the output ready flag of the fifo remains low until the third low-to-high transition of the synchro- nizing clock occurs, simultaneously forcing the output ready flag high and shifting the word to the fifo output register. in idt standard mode, from the time a word is written to a fifo, the empty flag will indicate the presence of data available for reading in a minimum of two cycles of the empty flag synchronizing clock. therefore, an empty flag is low if a word in memory is the next data to be sent to the flfo output register and two cycles of the port clock that reads data from the fifo have not elapsed since the time the word was written. the empty flag of the fifo remains low until the second low-to-high transition of the synchronizing clock occurs, forcing the empty flag high; only then can data be read. a low-to-high transition on an empty/output ready flag synchro- nizing clock begins the first synchronization cycle of a write if the clock transition occurs at time t skew1 or greater after the write. otherwise, the subsequent clock cycle can be the first synchronization cycle (see figures 11 and 12). full/input ready flags ( ff /ir) this is a dual purpose flag. in fwft mode, the input ready (ir) function is selected. in idt standard mode, the full flag ( ff ) function is selected. for both timing modes, when the full/input ready flag is high, a memory location is free in the fifo to receive new data. no memory locations are free when the full/input ready flag is low and attempted writes to the fifo are ignored. the full/input ready flag of a flfo is synchronized to the port clock that writes data to its array (clka). for both fwft and idt standard modes, each time a word is written to a fifo, its write pointer is incremented. the state machine that controls a full/input ready flag monitors a write pointer and read pointer comparator that indicates when the flfo memory status is full, full-1, or full-2. from the time a word is read from a fifo, its previous memory location is ready to be written to in a minimum of two cycles of the full/input ready flag synchronizing clock. therefore, an full/input ready flag is low if less than two cycles of the full/input ready flag synchroniz- ing clock have elapsed since the next memory write location has been read. the second low-to-high transition on the full/input ready flag synchronizing clock after the read sets the full/input ready flag high. a low-to-high transition on a full/input ready flag synchronizing clock begins the first synchronization cycle of a read if the clock transition occurs at time t skew 1 or greater after the read. otherwise, the subsequent clock cycle can be the first synchronization cycle (see figures 13 and 14). almost-empty flag ( ae ) the almost-empty flag of a fifo is synchronized to the port clock that reads data from its array (clkb). the state machine that controls an almost- empty flag monitors a write pointer and read pointer comparator that indicates when the fifo memory status is almost-empty, almost-empty+1, or almost-empty+2. the almost-empty state is defined by the contents of register x. these registers are loaded with preset values during a fifo reset, programmed from port a, or programmed serially (see almost- empty flag and almost-full flag offset programming section). an almost- empty flag is low when its fifo contains x or less words and is high when its fifo contains (x+1) or more words. note that a data word present in the fifo output register has been read from memory. two low-to-high transitions of the almost-empty flag synchronizing clock are required after a fifo write for its almost-empty flag to reflect the new level of fill. therefore, the almost-empty flag of a fifo containing (x+1) or more words remains low if two cycles of its synchronizing clock have not elapsed since the write that filled the memory to the (x+1) level. an almost-empty flag is set high by the second low-to-high transition of its synchronizing clock after the fifo write that fills memory to the (x+1) level. a low-to-high transition of an almost-empty flag synchronizing clock begins the first synchronization cycle if it occurs at time t skew2 or greater after the write that fills the fifo to (x+1) words. otherwise, the subsequent synchronizing clock cycle may be the first synchronization cycle. (see figure 15). almost-full flag ( af ) the almost-full flag of a fifo is synchronized to the port clock that writes data to its array. the state machine that controls an almost-full flag monitors a write pointer and read pointer comparator that indicates when the fifo memory status is almost-full, almost-full-1, or almost-full-2. the almost-full state is defined by the contents of register y. these registers are loaded with preset values during a flfo reset or, pro- grammed from port a, or programmed serially (see almost-empty flag and almost-full flag offset programming section). an almost-full flag is low when the number of words in its fifo is greater than or equal to (256-y) or (1,024-y) for the idt72v3623 or idt72v3643 respectively. an almost-full flag is high when the number of words in its fifo is less than or equal to [256-(y+1)] or [1,024-(y+1)] for the idt72v3623 or idt72v3643 respectively. note that a data word present in the fifo output register has been read from memory. two low-to-high transitions of the almost-full flag synchronizing clock are required after a fifo read for its almost-full flag to reflect the new level of fill. therefore, the almost-full flag of a fifo containing [256/ 1,024-(y+1)] or less words remains low if two cycles of its synchroniz- ing clock have not elapsed since the read that reduced the number of words in memory to [256/1,024-(y+1)]. an almost-full flag is set high by the second low-to-high transition of its synchronizing clock after the fifo read that reduces the number of words in memory to [256/1,024-(y+1)]. a low-to-high transition of an almost-full flag synchronizing clock begins the first synchronization cycle if it occurs at time t skew2 or greater after the read that reduces the number of words in memory to [256/1,024-(y+1)]. otherwise, the subsequent synchro- nizing clock cycle may be the first synchronization cycle (see figure 16). mailbox registers two 36-bit bypass registers are on the idt72v3623/72v3643 to pass command and control information between port a and port b without putting it in queue. the mailbox select (mba, mbb) inputs choose between a mail register and a fifo for a port data transfer operation. the usable width of both the mail1 and mail2 registers matches the selected bus size for port b. a low-to-high transition on clka writes data to the mail1 register when a port a write is selected by csa , w/ r a, and ena with mba high. if the selected port b bus size is 36 bits, the usable width of the mail1 register employs data lines a0-a35. if the selected port b bus size is 18 bits, then the usable width of the mail1 register employs data lines a0-a17. (in this case, a18-a35 are don?t care inputs.) if the selected port b bus size is 9 bits, then the usable width of the mail1 register employs data lines a0- a8. (in this case, a9-a35 are don?t care inputs.) a low-to-high transition on clkb writes b0-b35 data to the mail2 register when a port b write is selected by csb , w /rb, and enb with mbb high. if the selected port b bus size is 36 bits, the usable width of
14 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range the mail2 employs data lines b0-b35. if the selected port b bus size is 18 bits, then the usable width of the mail2 register employs data lines b0- b17. (in this case, b18-b35 are don?t care inputs.) if the selected port b bus size is 9 bits, then the usable width of the mail2 register employs data lines b0-b8. (in this case, b9-b35 are don?t care inputs.) writing data to a mail register sets its corresponding flag ( mbf1 or mbf2 ) low. attempted writes to a mail register are ignored while the mail flag is low. when data outputs of a port are active, the data on the bus comes from the fifo output register when the port mailbox select input is low and from the mail register when the port mailbox select input is high. the mail1 register flag ( mbf1 ) is set high by a low-to-high transition on clkb when a port b read is selected by csb , w /rb, and enb with mbb high. for a 36-bit bus size, 36 bits of mailbox data are placed on b0-b35. for an 18-bit bus size, 18 bits of mailbox data are placed on b0- b17. (in this case, b18-b35 are indeterminate.) for a 9-bit bus size, 9 bits of mailbox data are placed on b0-b8. (in this case, b9-b35 are indeterminate.) the mail2 register flag ( mbf2 ) is set high by a low-to-high transition on clka when a port a read is selected by csa , w/ r a, and ena with mba high. for a 36-bit bus size, 36 bits of mailbox data are placed on a0-a35. for an 18-bit bus size, 18 bits of mailbox data are placed on a0-a17. (in this case, a18-a35 are indeterminate.) for a 9-bit bus size, 9 bits of mailbox data are placed on a0-a8. (in this case, a9-a35 are indetermi- nate.) the data in a mail register remains intact after it is read and changes only when new data is written to the register. the endian select feature has no effect on mailbox data. for mail register and mail register flag timing diagrams, see figure 17 and 18. bus sizing the port b bus can be configured in a 36-bit long word, 18-bit word, or 9-bit byte format for data read from the fifo. the levels applied to the port b bus size select (size) and the bus-match select (bm) determine the port b bus size. these levels should be static throughout fifo operation. both bus size selections are implemented at the completion of reset, by the time the full/input ready flag is set high, as shown in figure 2. two different methods for sequencing data transfer are available for port b when the bus size selection is either byte-or word-size. they are referred to as big-endian (most significant byte first) and little-endian (least significant byte first). the level applied to the big-endian select (be) input during the low-to-high transition of rs1 selects the endian method that will be active during fifo operation. be is a don?t care input when the bus size selected for port b is long word. the endian method is implemented at the completion of reset, by the time the full/input ready flag is set high, as shown in figure 2. only 36-bit long word data is written to or read from the fifo memory on the idt72v3623/72v3643. bus-matching operations are done after data is read from the fifo ram. these bus-matching operations are not available when transferring data via mailbox registers. furthermore, both the word- and byte-size bus selections limit the width of the data bus that can be used for mail register operations. in this case, only those byte lanes belonging to the selected word- or byte-size bus can carry mailbox data. the remaining data outputs will be indeterminate. the remaining data inputs will be don?t care inputs. for example, when a word-size bus is selected, then mailbox data can be transmitted only between a0-a17 and b0-b17. when a byte-size bus is selected, then mailbox data can be transmitted only between a0-a8 and b0-b8. (see figures 17 and 18). bus-matching fifo reads data is read from the fifo ram in 36-bit long word increments. if a long word bus size is implemented, the entire long word immediately shifts to the fifo output register. if byte or word size is implemented on port b, only the first one or two bytes appear on the selected portion of the fifo output register, with the rest of the long word stored in auxiliary registers. in this case, subsequent fifo reads output the rest of the long word to the fifo output register in the order shown by figure 2. when reading data from fifo in byte or word format, the unused b0-b35 outputs are indeterminate.
15 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 figure 2. bus sizing a35 ? a27 a26 ? a18 a17 ? a9 a8 ? a0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 a a a d a c b b b c b d c c c a d d d b b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 (a) long word size (b) word size ? big-endian (c) word size ? little-endian (d) byte size ? big-endian write to fifo read from fifo 1st: read from fifo be bm size h h l l h l h h h x l x byte order on port a: b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 be bm size be bm size be bm size 2nd: read from fifo 3rd: read from fifo 4th: read from fifo b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 1st: read from fifo 1st: read from fifo 2nd: read from fifo 2nd: read from fifo d c (e) byte size ? little-endian 1st: read from fifo a b be bm size l h h 2nd: read from fifo 3rd: read from fifo 4th: read from fifo b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 4662 drw 04 byte order on port b: b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0 b35 ? b27 b26 ? b18 b17 ? b9 b8 ? b0
16 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range notes: 1. rs1 must be high during partial reset. 2. if be/ fwft is high, then ef /or will go low one clkb cycle earlier than in this case where be/ fwft is low. figure 4. partial reset (idt standard and fwft modes) notes: 1. prs must be high during reset. 2. if be/ fwft is high, then ef /or will go low one clkb cycle earlier than in this case where be/ fwft is low. figure 3. reset and loading x and y with a preset value of eight (idt standard and fwft modes) t rsf clka rs1 , rs2 ff /ir ae af mbf1 , mbf2 clkb ef /or fs1,fs0 4662 drw 05 t rsts t rsth t fsh t fss t wff t ref (2) t rsf 0,1 t rsf be be/ fwft spm fwft t bes t spms t spmh 1 2 t fws t beh t wff clka prs ff /ir ae af mbf1 , clkb ef /or 4662 drw 06 t rsts t rsth t wff t wff t ref t rsf t rsf t rsf mbf2 (2)
17 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 figure 6. serial programming of the almost-full flag and almost-empty flag offset values after reset (idt standard and fwft mod es) note: 1. csa = low, w/ r a = high, mba = low. figure 5. parallel programming of the almost-full flag and almost-empty flag offset values after reset (idt standard and fwft modes) notes: 1. it is not necessary to program offset register bits on consecutive clock cycles. fifo write attempts are ignored until ff /ir is set high. 2. programmable offsets are written serially to the sd input in the order af offset (y) and ae offset (x). 4662 drw 07 clka rs1 ff /ir a0-a35 fs1,fs0 ena t fsh t wff t enh t ens2 t ds t dh 4 0,0 af offset ( y ) ae offset (x) first word to fifo1 t fsh t fss spm t fss 1 2 clka ff /ir t sens t senh fs0/sd (2) t sph t sens t senh t fss t wff fs1/ sen ae offset ( x ) lsb t sds t sdh t sds t sdh af offset ( y ) msb rs1 4 t fss t fsh spm 4662 drw 08
18 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range note: 1. data read from the fifo note: 1. be is selected at reset: bm and size must be static throughout device operation. figure 8. port b long-word read cycle (idt standard and fwft modes) size mode (1) data written to fifo data read from fifo (select at reset) bm size be a35-a27 a26-a18 a17-a9 a8-a0 b35-b27 b26-b18 b17-b9 b8-b0 lxxa b c d a b c d data size table for fifo long-word reads note: 1. written to fifo. figure 7. port a write cycle timing for fifo (idt standard and fwft modes) 4662 drw09 clka ff /ira ena a0-a35 mba csa w/ r a t clkh t clkl t clk t ens1 t ds t enh t enh t enh t enh t dh w1 (1) w2 (1) t enh t enh no operation high t ens2 t ens2 t ens2 t ens2 t ens2 4662 drw 10 clkb ef /or enb mbb csb w /rb t dis t clk t clkh t clkl t a t mdv t en t a t enh t enh w1 (1) w2 (1) w3 (1) t enh t dis t en w2 (1) (1) w1 previous data t mdv t a or b0-b35 (standard mode) b0-b35 (fwft mode) t a no operation high t ens2 t ens2 t ens2
19 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 size mode (1) data written to fifo 1 read data read from fifo no. bm size be a35-a27 a26-a18 a17-a9 a8-a0 b17-b9 b8-b0 hl h a b c d1 a b 2c d hl l a b c d1 c d 2a b data size table for word reads figure 9. port b word read cycle timing (idt standard and fwft modes) note: 1. be is selected at reset: bm and size must be static throughout device operation. note: 1. unused word b18-b35 are indeterminate. clkb enb ff /or w /rb csb high 4662 drw 11 b0-b17 previous data t dis t a t a t enh no operation read 1 b0-b17 t a t a read 1 read 2 read 2 read 3 t dis mbb (standard mode) (fwft mode) or t en t mdv t mdv t en t ens2
20 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range bm size be a35-a27 a26-a18 a17-a9 a8-a0 b8-b0 hh h a b c d hh l a b c d 1 d 2 c 3 b 4 a figure 10. port b byte read cycle timing (idt standard and fwft modes) note: 1. be is selected at reset: bm and size must be static throughout device operation. size mode (1) data written to fifo read data read from fifo no. note: 1. unused bytes b9-b17, b18-b26, and b27-b35 are indeterminate. 1 a 2 b 3 c 4 d data size table for byte reads ef /or mbb csb w /rb enb clkb 4662 drw 12 high b0-b8 b0-b8 read 5 read 2 read 3 read 4 read 1 read 4 previous data read 2 no operation t dis t dis t a t a t a t a t a t a t enh t a t a read 1 (standard mode) (fwft mode) t en t mdv t mdv t en or read 3 t ens2
21 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 notes: 1. t skew1 is the minimum time between a rising clka edge and a rising clkb edge for or to transition high and to clock the next word to the fifo output register in three clkb cycles. if the time between the rising clka edge and rising clkb edge is less than t skew1 , then the transition of or high and load of the first word to the output register may occur one clkb cycle later than shown. 2. if port b size is word or byte, or is set low by the last word or byte read from the fifo, respectively. figure 11. or flag timing and first data word fall through when fifo is empty (fwft mode) csa w/ r a mba ir a0-a35 clkb or csb w /rb mbb ena enb b0-b35 clka 4662 drw13 12 3 t clkh t clkl t clk t enh t enh t ds t dh t skew1 t clk t clkl t ref t ref t enh t a old data in fifo output register w1 low high low high low t clkh w1 high (1) fifo empty t ens2 t ens2 t ens2
22 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range notes: 1. t skew1 is the minimum time between a rising clka edge and a rising clkb edge for ef to transition high in the next clkb cycle. if the time between the rising clka edge and rising clkb edge is less than t skew1 , then the transition of ef high may occur one clkb cycle later than shown. 2. if port b size is word or byte, ef is set low by the last word or byte read from the fifo, respectively. figure 12. ef ef ef ef ef flag timing and first data read when fifo is empty (idt standard mode) csa w/ r a mba ff a0-a35 clkb ef csb w /rb mbb ena enb b0-b35 clka 12 4662 drw14 t clkh t clkl t clk t enh t enh t ds t dh t skew1 t clk t clkl t enh t a w1 fifo empty low high low high low t clkh w1 high (1) t ref t ref t ens2 t ens2 t ens2
23 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 figure 13. ir flag timing and first available write when fifo is full (fwft mode) notes: 1. t skew1 is the minimum time between a rising clkb edge and a rising clka edge for ir to transition high in the next clka cycle. if th e time between the rising clkb edge and rising clka edge is less than t skew1 , then ir may transition high one clka cycle later than shown. 2. if port b size is word or byte, t skew1 is referenced to the rising clkb edge that reads the last word or byte write of the long word, respectively. csb or mbb enb b0-b35 clkb ir clka csa 4662 drw15 w/ r a 12 a0-a35 mba ena t clk t clkh t clkl t enh t a t skew1 t clk t clkh t clkl t ds t enh t enh t dh to fifo previous word in fifo output register next word from fifo low w /rb high low high low high (1) fifo full t wff t wff t ens2 t ens2 t ens2
24 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range notes: 1. t skew1 is the minimum time between a rising clkb edge and a rising clka edge for ff to transition high in the next clka cycle. if the time between the rising clkb edge and rising clka edge is less than t skew1 , then ff may transition high one clka cycle later than shown. 2. if port b size is word or byte, t skew1 is referenced from the rising clkb edge that reads the last word or byte of the long word, respectively. figure 14. ff ff ff ff ff flag timing and first available write when fifo is full (idt standard mode) notes: 1. t skew2 is the minimum time between a rising clka edge and a rising clkb edge for ae to transition high in the next clkb cycle. if the time between the rising clka edge and rising clkb edge is less than t skew2 , then ae may transition high one clkb cycle later than shown. 2. fifo write ( csa = low, w/ r a = low, mba = low), fifo read ( csb = low, w /rb = high, mbb = low). data in the fifo output register has been read from the fifo. 3. if port b size is word or byte, ae is set low by the last word or byte read from the fifo, respectively. figure 15. timing for ae ae ae ae ae when the fifo is almost-empty (idt standard and fwft modes). csb ef w /rb mbb enb b0-b35 clkb ff clka csa 4662 drw16 w/ r a a0-a35 mba ena 12 t clk t clkh t clkl t enh t a t skew1 t clk t clkl t ds t enh t enh t dh to fifo previous word in fifo output register next word from fifo low high low high low high (1) fifo full wff wff t t t clkh t ens2 t ens2 t ens2 ae clka enb 4662 drw 17 ena clkb 2 1 t enh t skew2 t pae t pae t enh x words in fifo (x+1) words in fifo (1) t ens2 t ens2
25 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 figure 17. timing for mail1 register and mbf1 mbf1 mbf1 mbf1 mbf1 flag (idt standard and fwft modes) note: 1. if port b is configured for word size, data can be written to the mail1 register using a0-a17 (a18-a35 are don't care inputs ). in this first case b0-b17 will have valid data (b18-b35 will be indeterminate). if port b is configured for byte size, data can be written to the mail1 register using a0-a8 (a9-a35 are don't care inputs). in this second case, b0-b8 will have valid data (b9-b35 will be indeterminate). notes: 1. t skew2 is the minimum time between a rising clka edge and a rising clkb edge for af to transition high in the next clka cycle. if the time between the rising clka edge and rising clkb edge is less than t skew2 , then af may transition high one clka cycle later than shown. 2. fifo write ( csa = low, w/ r a = high, mba = low), fifo read ( csb = low, w /rb = high, mbb = low). data in the fifo output register has been read from the fifo. 3. d = maximum fifo depth = 256 for the idt72v3623, 1,024 for the idt72v3643. 4. if port b size is word or byte, t skew2 is referenced from the rising clkb edge that reads the last word or byte of the long word, respectively. figure 16. timing for af af af af af when the fifo is almost-full (idt standard and fwft modes). af clka enb 4662 drw 18 ena clkb 12 t skew2 t enh t paf t enh t paf [d-(y+1)] words in fifo (d-y) words in fifo (1) t ens2 t ens2 4662 drw19 clka ena a0-a35 mba csa w/ r a clkb mbf1 csb mbb enb b0-b35 w /rb t enh t ds t dh t pmf t pmf t enh t dis t en t mdv t pmr fifo output register w1 (remains valid in mail1 register after read) t enh t enh t enh w1 t ens1 t ens2 t ens2 t ens2 t ens2
26 idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 commercial temperature range figure 18. timing for mail2 register and mbf2 mbf2 mbf2 mbf2 mbf2 flag (idt standard and fwft modes) note: 1. if port b is configured for word size, data can be written to the mail2 register using b0-b17 (b18-b35 are don't care inputs) . in this first case a0-a17 will have valid data (a18-a35 will be indeterminate). if port b is configured for byte size, data can be written to the mail2 register using b0-b8 (b9-b35 are don't care inputs). in this second case, a0-a8 will have valid data (a9-a35 will be indeterminate). figure 19. block diagram of 256 x 36, 1,024 x 36 synchronous fifo memory with programmable flags used in depth expansion configuration notes: 1. mailbox feature is not supported in depth expansion applications. (mba + mbb tie to gnd) 2. transfer clock should be set either to the write port clock (clka) or the read port clock (clkb), whichever is faster. 3. the amount of time it takes for ef /or of the last fifo in the chain to go high (i.e. valid data to appear on the last fifo?s outputs) after a word has been writt en to the first fifo is the sum of the delays for each individual fifo: (n - 1)*(4*transfer clock) + 3*t rclk , where n is the number of fifos in the expansion and t rclk is the clkb period. 4. the amount of time it takes for ff /ir of the first fifo in the chain to go high after a word has been read from the last fifo is the sum of the delays for each i ndividual fifo: (n - 1)*(3*transfer clock) + 2*t wclk , where n is the number of fifos in the expansion and t wclk is the clka period. 4662 drw20 clkb enb b0-b35 mbb csb w /rb clka mbf2 csa mba ena a0-a35 w/ r a t enh t ds t dh t enh t dis t en t mdv t pmr fifo output register w1 (remains valid in mail2 register after read) t enh t enh t enh t pmf t pmf w1 t ens2 t ens1 t ens2 t ens2 t ens2 data in (dn) read clock (clkb) read enable (enb) empty flag/ output ready ( ef /or) chip select ( csb ) data out (qn) transfer clock 4662 drw21 idt 72v3623 72v3643 v cc idt 72v3623 72v3643 write read a 0 -a 35 mba chip select ( csa ) write select (w/ r a) write enable (ena) almost-full flag ( af ) full flag/ input ready ( ff /ir) write clock (clka) clkb ef /or enb csb b 0 -b 35 w /rb mbb clka ena ff /ir csa mba a 0 -a 35 w/ r a read select ( w /rb) almost-empty flag ( ae ) b 0 -b 35 mbb v cc n n n qn dn v cc v cc
27 commercial temperature range idt72v3623/72v3643 cmos 3.3v syncbififo tm with bus-matching 256 x 36, 1,024 x 36 note: 1. includes probe and jig capacitance. figure 20. load circuit and voltage waveforms. 4662 drw 22 parameter measurement information from output under test 30 pf 330 3.3 v 510 propagation delay load circuit 3 v gnd timing input data, enable input gnd 3 v 1.5 v 1.5 v voltage waveforms setup and hold times voltage waveforms pulse durations voltage waveforms enable and disable times voltage waveforms propagation delay times 3 v gnd gnd 3 v 1.5 v 1.5 v 1.5 v 1.5 v t w output enable low-level output high-level output 3 v ol gnd 3 v 1.5 v 1.5 v 1.5 v 1.5 v oh ov gnd oh ol 1.5 v 1.5 v 1.5 v 1.5 v input in-phase output high-level input low-level input v v v v 1.5 v 3 v t s t h t plz t phz t pzl t pzh t pd t pd (1)
28 corporate headquarters for sales: for tech support: 6024 silver creek valley road 800-345-7015 or 408-284-8200 408-360-1753 san jose, ca 95138 fax: 408-284-2775 email: fifohelp@idt.com www.idt.com ordering information blank commercial (0 c to +70 c) xxxxxx device type x xx x x power speed package process/ temperature range x x blank 8 tube or tray tape and reel 4662 drw23 commercial only clock cycle time (t clk ) speed in nanoseconds thin quad flat pack (tqfp, pk128) 256 x 36 ? 3.3v syncfifo ? with bus-matching 1,024 x 36 ? 3.3v syncfifo ? with bus-matching low power 10 15 pf 72v3623 72v3643 l green g notes: 1. industrial temperature range is available by special order. 2. green parts available. for specific speeds and packages contact your sales office. datasheet document history 12/12/2000 pgs. 12 and 27. 03/21/2001 pgs. 6 and 7. 08/01/2001 pgs. 6, 8, 9 and 28. 10/22/2008 pg. 28. 05/24/2010 pgs. 1 and 28. 03/09/2015 pgs. 1-28.

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