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high-speed 16k x 16 dual-port static ram the idt logo is a registered trademark of integrated device technology, inc. features: ? true dual-ported memory cells which allow simulta- neous access of the same memory location ? high-speed access military: 25/35/55ns (max.) commercial: 20/25/35/55ns (max.) ? low-power operation idt7026s active: 750mw (typ.) standby: 5mw (typ.) idt7026l active: 750mw (typ.) standby: 1mw (typ.) ? separate upper-byte and lower-byte control for multiplexed bus compatibility ? idt7026 easily expands data bus width to 32 bits or more using the master/slave select when cascading more than one device ?m/ s = h for busy output flag on master, m/ s = l for busy input on slave ? on-chip port arbitration logic ? full on-chip hardware support of semaphore signaling between ports ? fully asynchronous operation from either port ? ttl-compatible, single 5v ( 10%) power supply ? available in 84-pin pga and 84-pin plcc ? industrial temperature range (C40 c to +85 c) is avail- able, tested to military electrical specifications military and commercial temperature ranges october 1996 ?1996 integrated device technology, inc. dsc 2939/3 1 functional block diagram idt7026s/l notes: 1. (master): busy is output; (slave): busy is input. 2. busy outputs are non-tri-stated push-pull. integrated device technology, inc. 6.17 for latest information contact idts web site at www.idt.com or fax-on-demand at 408-492-8391. i/o control address decoder memory array arbitration semaphore logic address decoder i/o control r/ w l busy l a 13l a 0l 2939 drw 01 ub l lb l ce l oe l i/o 8l -i/o 15l i/o 0l -i/o 7l ce l sem l m/ s r/ w r busy r ub r lb r ce r oe r i/o 8r -i/o 15r i/o 0r -i/o 7r a 13r a 0r sem r ce r (1,2) (1,2) 14 14
6.17 2 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges description: the idt7026 is a high-speed 16k x 16 dual-port static ram. the idt7026 is designed to be used as a stand-alone dual-port ram or as a combination master/slave dual- port ram for 32-bit-or-more word systems. using the idt master/slave dual-port ram approach in 32-bit or wider memory system applications results in full-speed, error-free operation without the need for additional discrete logic. this device provides two independent ports with separate control, address, and i/o pins that permit independent, asynchronous access for reads or writes to any location in memory. an automatic power down feature controlled by ce permits the on-chip circuitry of each port to enter a very low standby power mode. fabricated using idts cmos high-performance technol- ogy, these devices typically operate on only 750mw of power. the idt7026 is packaged in a ceramic 84-pin pga, and a 84-pin plcc. military grade product is manufactured in com- pliance with the latest revision of mil-std-883, class b, making it ideally suited to military temperature applications demanding the highest level of performance and reliability. pin configurations (1,2) notes: 1. all vcc pins must be connected to the power supply. 2. all gnd pins must be connected to the ground supply. 3. this text does not indicate orientation of the actual part-marking. 2939 drw 02 14 15 16 17 18 19 20 index 21 22 23 24 11109876543218483 33 34 35 36 37 38 39 40 41 42 43 44 45 v cc gnd i/o 8l a 8l 13 12 25 26 27 28 29 30 31 32 46 47 48 49 50 51 52 53 72 71 70 69 68 67 66 65 64 63 62 73 74 61 60 59 58 57 56 55 54 82 81 80 79 78 77 76 75 gnd busy l gnd idt7026 j84-1 84-pin plcc top view (3) a 0l m/ s a 0r i/o 9l i/o 10l i/o 11l i/o 12l i/o 13l i/o 14l i/o 15l i/o 0r i/o 1r i/o 2r v cc i/o 3r i/o 4r i/o 5r i/o 6r i/o 7r i/o 8r a 7l a 6l a 5l a 4l a 3l a 2l a 1l busy r a 1r a 3r a 4r a 5r a 6r a 7r a 2r i/o 7l i/o 6l i/o 5l i/o 4l i/o 3l i/o 2l v cc r/ w l sem l ce l ub l lb l a 12l gnd i/o 1l i/o 0l a 11l a 10l a 9l oe l i/o 9r i/o 10r i/o 11r i/o 12r i/o 13r i/o 14r gnd i/o 15r gnd a 12r a 11r a 10r a 9r a 8r oe r r/ w r sem r ce r ub r lb r a 13r a 13l
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 3 2939 tbl 01 left port right port names ce l ce r chip enable r/ w l r/ w r read/write enable oe l oe r output enable a 0l C a 13l a 0r C a 13r address i/o 0l C i/o 15l i/o 0r C i/o 15r data input/output sem l sem r semaphore enable ub l ub r upper byte select lb l lb r lower byte select busy l busy r busy flag m/ s master or slave select v cc power gnd ground pin names notes: 1. all v cc pins must be connected to power supply. 2. all gnd pins must be connected to ground supply. 3. this text does not indicate orientation of the actual part-marking. 2939 drw 03 i/o 7l 63 61 60 58 55 54 51 48 46 45 66 67 69 72 75 76 79 81 82 83 125 7 8 11 10 12 14 17 20 23 26 28 29 32 31 33 35 38 41 43 idt7026 g84-3 84-pin pga top view (3) abcdef ghj kl 42 59 56 49 50 40 25 27 30 36 34 37 39 84346915131618 22 24 19 21 68 71 70 77 80 ub r ce r gnd 11 10 09 08 07 06 05 04 03 02 01 64 65 62 57 53 52 47 44 73 74 78 gnd gnd r/ w r oe r lb r gnd gnd sem r ub l ce l r/ w l oe l gnd sem l v cc lb l a 13r busy r busy l m/ s a 13l a 11l index i/o 5l i/o 4l i/o 2l i/o 0l i/o 10l i/o 8l i/o 6l i/o 3l i/o 1l i/o 11l i/o 9l i/o 13l i/o 12l i/o 15l i/o 14l i/o 0r a 9l a 10l a 8l a 7l a 5l a 6l a 4l a 3l a 2l a 0l a 1l a 0r a 2r a 1r a 5r a 3r a 6r a 4r a 9r a 7r a 8r a 10r a 11r i/o 1r i/o 2r v cc i/o 3r i/o 4r i/o 5r i/o 7r i/o 6r i/o 9r i/o 8r i/o 11r i/o 10r i/o 12r i/o 13r i/o 14r i/o 15r v cc a 12r a 12l pin configurations (cont'd) (1,2) recommended operating temperature and supply voltage ambient grade temperature gnd v cc military C55 c to +125 c 0v 5.0v 10% commercial 0 c to +70 c 0v 5.0v 10% 2939 tbl 02
6.17 4 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges recommended dc operating condtions symbol parameter min. typ. max. unit v cc supply voltage 4.5 5.0 5.5 v gnd supply voltage 0 0 0 v v ih input high voltage 2.2 6.0 (2) v v il input low voltage C0.5 (1) 0.8 v notes: 2939 tbl 06 1. v il > -1.5v for pulse width less than 10ns. 2. v term must not exceed vcc + 0.5v. capacitance (1) (t a = +25 c, f = 1.0mhz) symbol parameter conditions (2) max. unit c in input capacitance v in = 3dv 9 pf c out output v out = 3dv 10 pf capacitance notes: 2939 tbl 07 1. this parameter is determined by device characterization but is not production tested. 2. 3dv represents the interpolated capacitance when the input and output signals switch from 0v to 3v or from 3v to 0v. absolute maximum ratings (1) symbol rating commercial military unit v term (2) terminal voltage C0.5 to +7.0 C0.5 to +7.0 v with respect to gnd t a operating 0 to +70 C55 to +125 c temperature t bias temperature C55 to +125 C65 to +135 c under bias t stg storage C55 to +125 C65 to +150 c temperature i out dc output 50 50 ma current notes: 2939 tbl 05 1. stresses greater than those listed under absolute maximum ratings may cause permanent damage to the device. this is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect reliability. 2. v term must not exceed vcc + 0.5v for more than 25% of the cycle time or 10ns maximum, and is limited to < 20ma for the period of v term > vcc + 0.5v. truth table i C non-contention read/write control inputs (1) outputs ce ce ce ce ce r/ w w w w w oe oe oe oe oe ub ub ub ub ub lb lb lb lb lb sem sem sem sem sem i/o 8-15 i/o 0-7 mode h x x x x h high-z high-z deselected: power-down x x x h h h high-z high-z both bytes deselected l l x l h h data in high-z write to upper byte only l l x h l h high-z data in write to lower byte only l l x l l h data in data in write to both bytes l h l l h h data out high-z read upper byte only l h l h l h high-z data out read lower byte only l h l l l h data out data out read both bytes x x h x x x high-z high-z outputs disabled note: 2939 tbl 03 1. a 0l a 13l 1 a 0r a 13r. truth table ii C semaphore read/write control (1) inputs outputs ce ce ce ce ce r/ w w w w w oe oe oe oe oe ub ub ub ub ub lb lb lb lb lb sem sem sem sem sem i/o 8-15 i/o 0-7 mode h h l x x l data out data out read data in semaphore flag x h l h h l data out data out read data in semaphore flag h x x x l data in data in write i/o 0 into semaphore flag x x h h l data in data in write i/o 0 into semaphore flag l x x l x l not allowed l x x x l l not allowed 2939 tbl 04 note: 1. there are eight semaphore flags written to via i/o 0 and read from all i/o's (i/o 0 -i/o 15 ). these eight semaphores are addressed by a 0 - a 2 .
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 5 dc electrical characteristics over the operating temperature and supply voltage range (v cc = 5.0v 10%) idt7026s idt7026l symbol parameter test conditions min. max. min. max. unit |i li | input leakage current (1) v cc = 5.5v, v in = 0v to v cc 105 m a |i lo | output leakage current ce = v ih , v out = 0v to v cc 105 m a v ol output low voltage i ol = 4ma 0.4 0.4 v v oh output high voltage i oh = C4ma 2.4 2.4 v note: 2939 tbl 08 dc electrical characteristics over the operating temperature and supply voltage range (1) (v cc = 5.0v 10%) 7026x20 7026x25 test com'l. only symbol parameter condition version typ. (2) max. typ. (2) max. unit i cc dynamic operating ce = v il , outputs open mil. s 170 345 ma current sem = v ih l 170 305 (both ports active) f = f max (3) coml. s 180 315 170 305 l 180 275 170 265 i sb1 standby current ce r = ce l = v ih mil. s 25 100 ma (both ports ttl sem r = sem l = v ih l2580 level inputs) f = f max (3) coml. s 30 85 25 85 l 30602560 i sb2 standby current ce "a" = v il and ce "b" = v ih (5) mil. s 105 230 ma (one port ttl active port outputs open, l 105 200 level inputs) f = f max (3) coml. s 115 210 105 200 sem r = sem l = v ih l 115 180 105 170 i sb3 full standby current both ports ce l and mil. s 1.0 30 ma (both ports all ce r > v cc - 0.2v l 0.2 10 cmos level inputs) v in > v cc - 0.2v or coml. s 1.0 15 1.0 15 v in < 0.2v, f = 0 (4) l 0.2 5 0.2 5 sem r = sem l > v cc - 0.2v i sb4 full standby current ce "a" < 0.2v and mil. s 100 200 ma (one port all ce "b" > v cc - 0.2v (5) l 100 175 cmos level inputs) sem r = sem l > v cc - 0.2v v in > v cc - 0.2v or coml. s 110 185 100 170 v in < 0.2v l 110 160 100 145 active port outputs open, f = f max (3) notes: 2939 tbl 09 1. "x" in part numbers indicates power rating (s or l). 2. v cc = 5v, t a = +25 c, and are not production tested. i ccdc = 120ma (typ.) 3. at f = f max , address and control lines (except output enable) are cycling at the maximum frequency read cycle of 1 / t rc, and using ac test conditions of input levels of gnd to 3v. 4. f = 0 means no address or control lines change. 5. port "a" may be either left or right port. port "b" is the opposite from port "a". 1. at vcc = 2.0v, input leakages are undefined.
6.17 6 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges dc electrical characteristics over the operating temperature and supply voltage range (1) (con't.) (v cc = 5.0v 10%) 7026x35 7026x55 test symbol parameter condition version typ. (2) max. typ. (2) max. unit i cc dynamic operating ce = v il , outputs open mil. s 160 335 150 310 ma current sem = v ih l 160 295 150 270 (both ports active) f = f max (3) coml. s 160 295 150 270 l 160 255 150 230 i sb1 standby current ce l = ce r = v ih mil. s 20 100 13 100 ma (both ports ttl sem r = sem l = v ih l 20801380 level inputs) f = f max (3) coml. s 20 85 13 85 l 20601360 i sb2 standby current ce "a" =v il and ce "b" =v ih (5) mil. s 95 215 85 195 ma (one port ttl active port outputs open, l 95 185 85 165 level inputs) f = f max (3) coml. s 95 185 85 165 sem r = sem l = v ih l 95 155 85 135 i sb3 full standby current both ports ce l and mil. s 1.0 30 1.0 30 ma (both ports all ce r > v cc - 0.2v l 0.2 10 0.2 10 cmos level inputs) v in > v cc - 0.2v or coml. s 1.0 15 1.0 15 v in < 0.2v, f = 0 (4) l 0.2 5 0.2 5 sem r = sem l >v cc - 0.2v i sb4 full standby current ce "a" < 0.2v and mil. s 90 190 80 175 ma (one port all ce "b" > v cc - 0.2v (5) l 90 165 80 150 cmos level inputs) sem r = sem l >v cc - 0.2v v in > v cc - 0.2v or coml. s 90 160 80 135 ma v in < 0.2v l 90 135 80 110 active port outputs open, f = f max (3) notes: 2939 tbl 10 1. "x" in part numbers indicates power rating (s or l). 2. v cc = 5v, t a = +25 c, and are not production tested. i ccdc = 120ma (typ.) 3. at f = f max , address and control lines (except output enable) are cycling at the maximum frequency read cycle of 1/ trc, and using ac test conditions of input levels of gnd to 3v. 4. f = 0 means no address or control lines change. 5. port "a" may be either left or right port. port "b" is the opposite from port "a".
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 7 idt7026x35 idt7026x55 symbol parameter min. max. min. max. unit read cycle t rc read cycle time 35 55 ns t aa address access time 35 55 ns t ace chip enable access time (3) 3555ns t abe byte enable access time (3) 3555ns t aoe output enable access time 20 30 ns t oh output hold from address change 3 3 ns t lz output low-z time (1, 2) 33ns t hz output high-z time (1, 2) 1525ns t pu chip enable to power up time (2) 00ns t pd chip disable to power down time (2) 3550ns t sop semaphore flag update pulse ( oe or sem )1515ns t saa semaphore address access time 35 55 ns ac test conditions input pulse levels gnd to 3.0v input rise/fall times 5ns max. input timing reference levels 1.5v output reference levels 1.5v output load figures 1 and 2 2939 tbl 11 ac electrical characteristics over the operating temperature and supply voltage range (4) idt7026x20 idt7026x25 com'l. only symbol parameter min. max. min. max. unit read cycle t rc read cycle time 20 25 ns t aa address access time 20 25 ns t ace chip enable access time (3) 2025ns t abe byte enable access time (3) 2025ns t aoe output enable access time 12 13 ns t oh output hold from address change 3 3 ns t lz output low-z time (1, 2) 33ns t hz output high-z time (1, 2) 1215ns t pu chip enable to power up time (2) 00ns t pd chip disable to power down time (2) 2025ns t sop semaphore flag update pulse ( oe or sem )1012ns t saa semaphore address access time 20 25 ns 2939 tbl 12 2939 drw 05 893 w 30pf 347 w 5v data out busy int 893 w 5pf 347 w 5v data out 2939 drw 04 figure 1. ac output load figure 2. output test load (for t lz , t hz , t wz , t ow ) * including scope and jig. notes: 1. transition is measured 200mv from low or high-impedance voltage with output test load (figure 2). 2. this parameter is guaranteed by device characterization, but is not production tested. 3. to access ram, ce = v il and sem = v ih . to access semaphore, ce = v ih and sem = v il . 4. "x" in part numbers indicates power rating (s or l).
6.17 8 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges notes: 1. timing depends on which signal is asserted last, oe , ce , lb , or ub . 2. timing depends on which signal is de-asserted first ce , oe , lb , or ub . 3. t bdd delay is required only in cases where the opposite port is completing a write operation to the same address location. for simultaneous read operations busy has no relation to valid output data. 4. start of valid data depends on which timing becomes effective last t aoe , t ace , t aa or t bdd . 5. sem = v ih . waveform of read cycles (5) t rc r/ w ce addr t aa oe ub , lb 2939 drw 06 (4) t ace (4) t aoe (4) t abe (4) (1) t lz t oh (2) t hz (3, 4) t bdd data out busy out valid data (4) timing of power-up power-down ce 2939 drw 07 t pu i cc i sb t pd 50% 50%
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 9 ac electrical characteristics over the operating temperature and supply voltage (5) idt7026x20 idt7026x25 com'l. only symbol parameter min. max. min. max. unit write cycle t wc write cycle time 20 25 ns t ew chip enable to end-of-write (3) 15 20 ns t aw address valid to end-of-write 15 20 ns t as address set-up time (3) 00ns t wp write pulse width 15 20 ns t wr write recovery time 0 0 ns t dw data valid to end-of-write 15 15 ns t hz output high-z time (1, 2) 1215ns t dh data hold time (4) 00ns t wz write enable to output in high-z (1, 2) 1215ns t ow output active from end-of-write (1, 2, 4) 00ns t swrd sem flag write to read time 5 5 ns t sps sem flag contention window 5 5 ns idt7026x35 idt7026x55 symbol parameter min. max. min. max. unit write cycle t wc write cycle time 35 55 ns t ew chip enable to end-of-write (3) 30 45 ns t aw address valid to end-of-write 30 45 ns t as address set-up time (3) 00ns t wp write pulse width 25 40 ns t wr write recovery time 0 0 ns t dw data valid to end-of-write 15 30 ns t hz output high-z time (1, 2) 1525ns t dh data hold time (4) 00ns t wz write enable to output in high-z (1, 2) 1525ns t ow output active from end-of-write (1, 2, 4) 00ns t swrd sem flag write to read time 5 5 ns t sps sem flag contention window 5 5 ns notes: 2939 tbl 13 1. transition is measured 200mv from low or high-impedance voltage with output test load (figure 2). 2. this parameter is guaranteed by device characterization, but is not production tested. 3. to access ram, ce = v il and sem = v ih . to access semaphore, ce = v ih and sem = v il . either condition must be valid for the entire t ew time. 4. the specification for t dh must be met by the device supplying write data to the ram under all operating conditions. although t dh and t ow values will vary over voltage and temperature, the actual t dh will always be smaller than the actual t ow . 5. "x" in part numbers indicates power rating (s or l).
6.17 10 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges timing waveform of write cycle no. 1, r/ w w w w w controlled timing (1,5,8) notes: 1. r/ w or ce or ub and lb must be high during all address transitions. 2. a write occurs during the overlap (t ew or t wp ) of a low ce and a low r/ w for memory array writing cycle. 3. t wr is measured from the earlier of ce or r/ w (or sem or r/ w ) going high to the end of write cycle. 4. during this period, the i/o pins are in the output state and input signals must not be applied. 5. if the ce or sem low transition occurs simultaneously with or after the r/ w low transition, the outputs remain in the high-impedance state. 6. timing depends on which enable signal is asserted last, ce or r/ w . 7. this parameter is guaranteed by device characterization, but is not production tested. transition is measured + 200mv from steady state with the output test load (figure 2). 8. if oe is low during r/ w controlled write cycle, the write pulse width must be the larger of t wp or (t wz + t dw ) to allow the i/o drivers to turn off and data to be placed on the bus for the required t dw . if oe is high during an r/ w controlled write cycle, this requirement does not apply and the write pulse can be as short as the specified t wp . 9. to access ram, ce = v il and sem = v ih . to access semaphore, ce = v ih and sem = v il . t ew must be met for either condition. timing waveform of write cycle no. 2, ce ce ce ce ce , ub ub ub ub ub , lb lb lb lb lb controlled timing (1,5) r/ w t wc t hz t aw t wr t as t wp data out (2) t wz t dw t dh t ow oe address data in (6) (4) (4) (7) ub or lb 2939 drw 08 (9) ce or sem (9) (7) (3) 2939 drw 09 t wc t as t wr t dw t dh address data in r/ w t aw t ew ub or lb (3) (2) (6) ce or sem (9) (9)
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 11 timing waveform of semaphore read after write timing, either side (1) timing waveform of semaphore write contention (1,3,4) notes: 1. ce = v ih or ub and lb = v ih for the duration of the above timing (both write and read cycle). 2. "data out valid" represents all i/o's (i/o 0 -i/o 15 ) equal to the semaphore value. sem "a" 2939 drw 11 t sps match r/ w "a" match a 0"a" -a 2"a" side ? (2) sem "b" r/ w "b" a 0"b" -a 2"b" side (2) ? notes: 1. d or = d ol = v il , ce r = ce l = v ih , or both ub & lb = v ih . 2. all timing is the same for left and right ports. port a may be either left or right port. port b is the opposite from port a. 3. this parameter is measured from r/ w" a" or sem" a" going high to r/ w" b" or sem" b" going high. 4. if t sps is not satisfied, there is no guarantee which side will be granted the semaphore flag. sem 2939 drw 10 t aw t ew t sop i/o 0 valid address t saa r/ w t wr t oh t ace valid address data in valid data out t dw t wp t dh t as t swrd t aoe read cycle write cycle a 0 -a 2 oe valid (2)
6.17 12 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges busy timing (m/ s s s s s = v il ) t wb busy input to write (4) 00ns t wh write hold after busy (5) 25 25 ns port-to-port delay timing t wdd write pulse to data delay (1) 6080ns t ddd write data valid to read data delay (1) 4565ns ac electrical characteristics over the operating temperature and supply voltage range (6) idt7026x20 idt7026x25 com'l. only symbol parameter min. max. min. max. unit busy timing (m/ s s s s s = v ih ) t baa busy access time from address match 20 20 ns t bda busy disable time from address not matched 20 20 ns t bac busy access time from chip enable low 20 20 ns t bdc busy disable time from chip enable high 17 17 ns t aps arbitration priority set-up time (2) 55ns t bdd busy disable to valid data (3) 3030ns t wh write hold after busy (5) 15 17 ns busy timing (m/ s s s s s = v il ) t wb busy input to write (4) 00ns t wh write hold after busy (5) 15 17 ns port-to-port delay timing t wdd write pulse to data delay (1) 4550ns t ddd write data valid to read data delay (1) 3035ns idt7026x35 idt7026x55 symbol parameter min. max. min. max. unit busy timing (m/ s s s s s = v ih ) t baa busy access time from address match 20 45 ns t bda busy disable time from address not matched 20 40 ns t bac busy access time from chip enable low 20 40 ns t bdc busy disable time from chip enable high 20 35 ns t aps arbitration priority set-up time (2) 55ns t bdd busy disable to valid data (3) 3540ns t wh write hold after busy (5) 25 25 ns notes: 2939 tbl 15 1. port-to-port delay through ram cells from writing port to reading port, refer to "timing waveform of write with port-to-port read and busy (m/ s = v ih )". 2. to ensure that the earlier of the two ports wins. 3. t bdd is a calculated parameter and is the greater of 0, t wdd C t wp (actual), or t ddd C t dw (actual). 4. to ensure that the write cycle is inhibited on port "b" during contention on port "a". 5. to ensure that a write cycle is completed on port "b" after contention on port "a". 6. "x" in part numbers indicates power rating (s or l).
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 13 timing waveform of write with port-to-port read and busy busy busy busy busy (m/ s s s s s = v ih ) (2,4,5) 2939 drw 12 t dw t aps addr "a" t wc data out "b" match t wp r/ w "a" data in "a" addr "b" t dh valid (1) match busy "b" t bda valid t bdd t ddd (3) t wdd t baa notes: 1. to ensure that the earlier of the two ports wins. t aps is ignored for m/ s = v il (slave). 2. ce l = ce r = v il. 3. oe = v il for the reading port. 4. if m/ s = v il (slave), busy is an input. then for this example busy "a" = v ih and busy "b" input is shown above. 5. all timing is the same for left and right ports. port "a" may be either the left or right port. port "b" is the port opposite from port "a". timing waveform of write with busy (m/ s s s s s = v il ) notes: 1. t wh must be met for both busy input (slave) and output (master). 2. busy is asserted on port "b" blocking r/ w "b" , until busy "b" goes high. 2939 drw 13 r/ w "a" busy "b" t wp t wb r/ w "b" t wh (2) (3) (1)
6.17 14 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges waveform of busy arbitration controlled by ce ce ce ce ce timing (m/ s s s s s = v ih ) (1) waveform of busy arbitration cycle controlled by address match timing (m/ s s s s s = v ih ) (1) 2939 drw 15 addr "a" and "b" addresses match ce "a" ce "b" busy "b" t aps t bac t bdc (2) 2939 drw 15 addr "a" address "n" addr "b" busy "b" t aps t baa t bda (2) matching address "n" notes: 1. all timing is the same for left and right ports. port a may be either the left or right port. port b is the port opposite from a. 2. if t aps is not satisfied, the busy signal will be asserted on one side or another but there is no guarantee on which side busy will be asserted. truth table iii example of semaphore procurement sequence (1,2) functions d 0 - d 15 left d 0 - d 15 right status no action 1 1 semaphore free left port writes "0" to semaphore 0 1 left port has semaphore token right port writes "0" to semaphore 0 1 no change. right side has no write access to semaphore left port writes "1" to semaphore 1 0 right port obtains semaphore token left port writes "0" to semaphore 1 0 no change. left port has no write access to semaphore right port writes "1" to semaphore 0 1 left port obtains semaphore token left port writes "1" to semaphore 1 1 semaphore free right port writes "0" to semaphore 1 0 right port has semaphore token right port writes "1" to semaphore 1 1 semaphore free left port writes "0" to semaphore 0 1 left port has semaphore token left port writes "1" to semaphore 1 1 semaphore free notes: 2683 tbl 16 1. this table denotes a sequence of events for only one of the eight semaphores on the idt7026. 2. there are eight semaphore flags written to via i/o 0 and read from all i/o's (i/o 0 -i/o 15 ). these eight semaphores are addressed by a 0 - a 2 .
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 15 functional description the idt7026 provides two ports with separate control, address and i/o pins that permit independent access for reads or writes to any location in memory. the idt7026 has an automatic power down feature controlled by ce . the ce controls on-chip power down circuitry that permits the respective port to go into a standby mode when not selected ( ce high). when a port is enabled, access to the entire memory array is permitted. busy logic busy logic provides a hardware indication that both ports of the ram have accessed the same location at the same time. it also allows one of the two accesses to proceed and signals the other side that the ram is busy. the busy pin can then be used to stall the access until the operation on the other side is completed. if a write operation has been attempted from the side that receives a busy indication, the write signal is gated internally to prevent the write from proceeding. the use of busy logic is not required or desirable for all applications. in some cases it may be useful to logically or the busy outputs together and use any busy indication as an interrupt source to flag the event of an illegal or illogical operation. if the write inhibit function of busy logic is not desirable, the busy logic can be disabled by placing the part in slave mode with the m/ s pin. once in slave mode the busy pin operates solely as a write inhibit input pin. normal opera- tion can be programmed by tying the busy pins high. if desired, unintended write operations can be prevented to a port by tying the busy pin for that port low. the busy outputs on the idt 7026 ram in master mode, are push-pull type outputs and do not require pull up resistors to operate. if these rams are being expanded in depth, then the busy indication for the resulting array requires the use of an external and gate. truth table iv address busy arbitration inputs outputs a 0l -a 13l ce ce ce ce ce l ce ce ce ce ce r a 0r -a 13r busy busy busy busy busy l (1) busy busy busy busy busy r (1) function xx no match h h normal hx match h h normal xh match h h normal ll match (2) (2) write inhibit (3) notes: 2683 tbl 17 1. pins busy l and busy r are both outputs when the part is configured as a master. both are inputs when configured as a slave. busy x outputs on the idt7026 are push pull, not open drain outputs. on slaves the busy x input internally inhibits writes. 2. low if the inputs to the opposite port were stable prior to the address and enable inputs of this port. high if the inputs to the opposite port became stable after the address and enable inputs of this port. if t aps is not met, either busy l or busy r = low will result. busy l and busy r outputs cannot be low simultaneously. 3. writes to the left port are internally ignored when busy l outputs are driving low regardless of actual logic level on the pin. writes to the right port are internally ignored when busy r outputs are driving low regard- less of actual logic level on the pin. if two or more master parts were used when expanding in width, a split decision could result with one master indicating busy on one side of the array and another master indicating busy on one other side of the array. this would inhibit the write operations from one port for part of a word and inhibit the write operations from the other port for the other part of the word. the busy arbitration, on a master, is based on the chip enable and address signals only. it ignores whether an access is a read or write. in a master/slave array, both address and chip enable must be valid long enough for a busy flag to be output from the master before the actual write pulse can be initiated with either the r/ w signal or the byte enables. failure to observe this timing can result in a glitched internal write inhibit signal and corrupted data in the slave. semaphores the idt7026 is an extremely fast dual-port 16k x 16 cmos static ram with an additional 8 address locations dedicated to binary semaphore flags. these flags allow either processor on the left or right side of the dual-port ram to claim a privilege over the other processor for functions defined by the system designers software. as an example, the sema- phore can be used by one processor to inhibit the other from accessing a portion of the dual-port ram or any other shared resource. the dual-port ram features a fast access time, and both ports are completely independent of each other. this means that the activity on the left port in no way slows the access time of the right port. both ports are identical in function to standard width expansion with busy logic master/slave arrays when expanding an idt7026 ram array in width while using busy logic, one master part is used to decide which side of the ram array will receive a busy indication, and to output that indication. any number of slaves to be addressed in the same address range as the master, use the busy signal as a write inhibit signal. thus on the idt7026 ram the busy pin is an output if the part is used as a master (m/ s pin = h), and the busy pin is an input if the part used as a slave (m/ s pin = l) as shown in figure 3. 2939 drw 16 master dual port ram busy l busy r ce master dual port ram busy l busy r ce slave dual port ram busy l busy r ce slave dual port ram busy l busy r ce busy l busy r decoder figure 3. busy and chip enable routing for both width and depth expansion with idt7026 rams.
6.17 16 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges cmos static ram and can be read from, or written to, at the same time with the only possible conflict arising from the simultaneous writing of, or a simultaneous read/write of, a non-semaphore location. semaphores are protected against such ambiguous situations and may be used by the system program to avoid any conflicts in the non-semaphore portion of the dual-port ram. these devices have an automatic power-down feature controlled by ce , the dual-port ram enable, and sem , the semaphore enable. the ce and sem pins control on-chip power down circuitry that permits the respective port to go into standby mode when not selected. this is the condition which is shown in truth table where ce and sem are both high. systems which can best use the idt7026 contain multiple processors or controllers and are typically very high-speed systems which are software controlled or software intensive. these systems can benefit from a performance increase offered by the idt7026's hardware semaphores, which pro- vide a lockout mechanism without requiring complex pro- gramming. software handshaking between processors offers the maximum in system flexibility by permitting shared resources to be allocated in varying configurations. the idt7026 does not use its semaphore flags to control any resources through hardware, thus allowing the system designer total flexibility in system architecture. an advantage of using semaphores rather than the more common methods of hardware arbitration is that wait states are never incurred in either processor. this can prove to be a major advantage in very high-speed systems. how the semaphore flags work the semaphore logic is a set of eight latches which are independent of the dual-port ram. these latches can be used to pass a flag, or token, from one port to the other to indicate that a shared resource is in use. the semaphores provide a hardware assist for a use assignment method called token passing allocation. in this method, the state of a semaphore latch is used as a token indicating that shared resource is in use. if the left processor wants to use this resource, it requests the token by setting the latch. this processor then verifies its success in setting the latch by reading it. if it was successful, it proceeds to assume control over the shared resource. if it was not successful in setting the latch, it determines that the right side processor has set the latch first, has the token and is using the shared resource. the left processor can then either repeatedly request that semaphores status or remove its request for that semaphore to perform another task and occasionally attempt again to gain control of the token via the set and test sequence. once the right side has relinquished the token, the left side should succeed in gaining control. the semaphore flags are active low. a token is re- quested by writing a zero into a semaphore latch and is released when the same side writes a one to that latch. the eight semaphore flags reside within the idt7026 in a separate memory space from the dual-port ram. this address space is accessed by placing a low input on the sem pin (which acts as a chip select for the semaphore flags) and using the other control pins (address, oe , and r/ w ) as they would be used in accessing a standard static ram. each of the flags has a unique address which can be accessed by either side through address pins a0 C a2. when accessing the semaphores, none of the other address pins has any effect. when writing to a semaphore, only data pin d 0 is used. if a low level is written into an unused semaphore location, that flag will be set to a zero on that side and a one on the other side (see table iii). that semaphore can now only be modified by the side showing the zero. when a one is written into the same location from the same side, the flag will be set to a one for both sides (unless a semaphore request from the other side is pending) and then can be written to by both sides. the fact that the side which is able to write a zero into a semaphore subsequently locks out writes from the other side is what makes semaphore flags useful in interprocessor communica- tions. (a thorough discussing on the use of this feature follows shortly.) a zero written into the same location from the other side will be stored in the semaphore request latch for that side until the semaphore is freed by the first side. when a semaphore flag is read, its value is spread into all data bits so that a flag that is a one reads as a one in all data bits and a flag containing a zero reads as all zeros. the read value is latched into one sides output register when that side's semaphore select ( sem ) and output enable ( oe ) signals go active. this serves to disallow the semaphore from changing state in the middle of a read cycle due to a write cycle from the other side. because of this latch, a repeated read of a semaphore in a test loop must cause either signal ( sem or oe ) to go inactive or the output will never change. a sequence write/read must be used by the sema- phore in order to guarantee that no system level contention will occur. a processor requests access to shared resources by attempting to write a zero into a semaphore location. if the semaphore is already in use, the semaphore request latch will contain a zero, yet the semaphore flag will appear as one, a fact which the processor will verify by the subsequent read (see table iii). as an example, assume a processor writes a zero to the left port at a free semaphore location. on a subsequent read, the processor will verify that it has written successfully to that location and will assume control over the resource in question. meanwhile, if a processor on the right side attempts to write a zero to the same semaphore flag it will fail, as will be verified by the fact that a one will be read from that semaphore on the right side during subsequent read. had a sequence of read/write been used instead, system contention problems could have occurred during the gap between the read and write cycles. it is important to note that a failed semaphore request must be followed by either repeated reads or by writing a one into the same location. the reason for this is easily understood by looking at the simple logic diagram of the semaphore flag in figure 4. two semaphore request latches feed into a sema- phore flag. whichever latch is first to present a zero to the semaphore flag will force its side of the semaphore flag low and the other side high. this condition will continue until a
idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 6.17 17 d 2939 drw 17 0 d q write d 0 d q write semaphore request flip flop semaphore request flip flop l port r port semaphore read semaphore read dual-port ram, the processor on the left port could write and then read a zero in to semaphore 0. if this task were success- fully completed (a zero was read back rather than a one), the left processor would assume control of the lower 8k. mean- while the right processor was attempting to gain control of the resource after the left processor, it would read back a one in response to the zero it had attempted to write into semaphore 0. at this point, the software could choose to try and gain control of the second 8k section by writing, then reading a zero into semaphore 1. if it succeeded in gaining control, it would lock out the left side. once the left side was finished with its task, it would write a one to semaphore 0 and may then try to gain access to semaphore 1. if semaphore 1 was still occupied by the right side, the left side could undo its semaphore request and perform other tasks until it was able to write, then read a zero into semaphore 1. if the right processor performs a similar task with semaphore 0, this protocol would allow the two processors to swap 8k blocks of dual-port ram with each other. the blocks do not have to be any particular size and can even be variable, depending upon the complexity of the software using the semaphore flags. all eight semaphores could be used to divide the dual-port ram or other shared resources into eight parts. semaphores can even be assigned different meanings on different sides rather than being given a common meaning as was shown in the example above. semaphores are a useful form of arbitration in systems like disk interfaces where the cpu must be locked out of a section of memory during a transfer and the i/o device cannot tolerate any wait states. with the use of semaphores, once the two devices has determined which memory area was off-limits to the cpu, both the cpu and the i/o devices could access their assigned portions of memory continuously without any wait states. semaphores are also useful in applications where no memory wait state is available on one or both sides. once a semaphore handshake has been performed, both proces- sors can access their assigned ram segments at full speed. another application is in the area of complex data struc- tures. in this case, block arbitration is very important. for this application one processor may be responsible for building and updating a data structure. the other processor then reads and interprets that data structure. if the interpreting processor reads an incomplete data structure, a major error condition may exist. therefore, some sort of arbitration must be used between the two different processors. the building processor arbitrates for the block, locks it and then is able to go in and update the data structure. when the update is completed, the data structure block is released. this allows the interpreting processor to come back and read the complete data structure, thereby guaranteeing a consistent data structure. one is written to the same semaphore request latch. should the other sides semaphore request latch have been written to a zero in the meantime, the semaphore flag will flip over to the other side as soon as a one is written into the first sides request latch. the second sides flag will now stay low until its semaphore request latch is written to a one. from this it is easy to understand that, if a semaphore is requested and the processor which requested it no longer needs the resource, the entire system can hang up until a one is written into that semaphore request latch. the critical case of semaphore timing is when both sides request a single token by attempting to write a zero into it at the same time. the semaphore logic is specially designed to resolve this problem. if simultaneous requests are made, the logic guarantees that only one side receives the token. if one side is earlier than the other in making the request, the first side to make the request will receive the token. if both requests arrive at the same time, the assignment will be arbitrarily made to one port or the other. one caution that should be noted when using semaphores is that semaphores alone do not guarantee that access to a resource is secure. as with any powerful programming technique, if semaphores are misused or misinterpreted, a software error can easily happen. initialization of the semaphores is not automatic and must be handled via the initialization program at power-up. since any semaphore request flag which contains a zero must be reset to a one, all semaphores on both sides should have a one written into them at initialization from both sides to assure that they will be free when needed. using semaphoressome examples perhaps the simplest application of semaphores is their application as resource markers for the idt7026s dual-port ram. say the 16k x 16 ram was to be divided into two 8k x 16 blocks which were to be dedicated at any one time to servicing either the left or right port. semaphore 0 could be used to indicate the side which would control the lower section of memory, and semaphore 1 could be defined as the indicator for the upper section of memory. to take a resource, in this example the lower 8k of figure 4. idt7026 semaphore logic
6.17 18 idt7026s/l high-speed 16k x 16 dual-port static ram military and commercial temperature ranges 2939 drw 18 a power 999 speed a package a process/ temperature range blank commercial (0 c to +70 c) b military (?5 c to +125 c) compliant to mil-std-883, class b g j 84-pin pga (g84-3) 84-pin plcc (j84-1) s l standard power low power xxxxx device type 256k (16k x 16) dual-port ram 7026 idt 20 25 35 55 commercial only speed in nanoseconds ordering information

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