IDT71342LA70J

HIGH SPEED 4K X 8 DUAL-PORT STATIC RAM WITH SEMAPHORE Features ◆ IDT71342SA/LA ◆ High-speed access – Commercial: 20/25/35/45/55/70ns (max.) – Industrial: 25/35/55ns (max.) Low-power operation – IDT71342SA Active: 700mW (typ.) Standby: 5mW (typ.) – IDT71342LA Active: 700mW (typ.) Standby: 1mW (typ.) ◆ ◆ ◆ ◆ ◆ ◆ Fully asynchronous operation from either port Full on-chip hardware support of semaphore signalling between ports Battery backup operation—2V data retention (LA only) TTL-compatible; single 5V (±10%) power supply Available in plastic packages Industrial temperature range (–40°C to +85°C) is available for selected speeds Functional Block Diagram R/WL CEL R/WR CER OEL I/O CONTROL I/O CONTROL OER I/O0L- I/O7L I/O0R - I/O7R MEMORY ARRAY SEMAPHORE LOGIC SEML ADDRESS DECODER ADDRESS DECODER SEMR A0L- A11L A0R- A11R 2721 drw 01 JANUARY 2001 1 ©2000 Integrated Device Technology, Inc. DSC 2621/12 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges Description The IDT71342 is a high-speed 4K x 8 Dual-Port Static RAM with full on-chip hardware support of semaphore signalling between the two ports. The IDT71342 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. To assist in arbitrating between ports, a fully independent semaphore logic block is provided. This block contains unassigned flags which can be accessed by either side; however, only one side can control the flag at any time. An automatic power down feature, controlled by CE and SEM, permits the on-chip circuitry of each port to enter a very low standby power mode (both CE and SEM HIGH). Fabricated using IDT’s CMOS high-performance technology, this device typically operates on only 700mW of power. Low-power (LA) versions offer battery backup data retention capability, with each port typically consuming 200µW from a 2V battery. The device is packaged in either a 64-pin TQFP or a 52-pin PLCC. Pin Configurations(1,2,3) R/WR SEMR A11R SEML R/WL CEL INDEX 765 A1L A2L A3L A4L A5L A6L A7L A8L A9L I/O0L I/O1L I/O2L I/O3L 8 9 10 11 12 13 14 15 16 17 18 19 20 43 2 1 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 OER A0R A1R A2R A3R A4R A5R A6R A7R A8R A9R N/C I/O7R IDT71342J J52-1(4) 52-Pin PLCC Top View(5) 21 22 23 24 25 26 27 28 29 30 31 32 33 I/O5L N/C GND I/O0R I/O1R I/O2R I/O4R I/O5R I/O3R I/O6R I/O4L I/O6L I/O7L VCC CER A10R OEL A10L A11L A0L 2721 drw 02 INDEX OEL A0L A1L A2L A3L A4L A5L A6L N/C A7L A8L A9L N/C I/O0L I/O1L I/O2L 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 N/C N/C A10L A11L SEML R/WL CEL VCC N/C CER R/WR SEM R A11R A10R N/C N/C NOTES: 1. All Vcc pins must be connected to power supply. 2. All GND pins must be connected to ground supply. 3. J52 package body is approximately .79 in x .79 in x .17 in. PN64 package body is approximately 14mm x 14mm x 1.4mm. 4. This package code is used to reference the package diagram. 5. This text does not indicate orientation of the actual part-marking. I/O3L N/C I/O4L I/O5L I/O6L I/O7L N/C N/C GND I/O0R I/O1R I/O2R I/O3R N/C I/O4R I/O5R 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 71342PF PN64-1(4) 64-Pin TQFP Top View(5) 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 OER A0R A1R A2R A3R A4R A5R A6R N/C A7R A8R A9R N/C N/C I/O7R I/O6R 2721 drw 03 6.42 2 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges Absolute Maximum Ratings(1) Symbol VTERM(2) Rating Terminal Voltage with Respect to GND Temperature Under Bias Storage Temperature Power Dissipation DC Output Current Commercial & Industrial -0.5 to +7.0 Unit V Maximum Operating Temperature and Supply Voltage(1,2) Grade Commercial Ambient Temperature 0OC to +70OC -40 C to +85 C O O GND 0V 0V Vcc 5.0V + 10% 5.0V + 10% 2721 tbl 03 TBIAS TSTG PT(3) IOUT -55 to +125 -65 to +150 1.5 50 o C C Industrial o NOTES: 1. This is the parameter TA. This is the "instant on" case temperature. W mA 2721 tbl 01 NOTES: 1. Stresses greater than those listed under ABSOLUTE MAXIMUM RATINGS may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect reliability. 2. VTERM must not exceed Vcc + 10% for more than 25% of the cycle time or 10 ns maximum, and is limited to < 20mA for the period of VTERM > Vcc +10%. Recommended DC Operating Conditions Symbol VCC GND VIH VIL Parameter Supply Voltage Ground Input High Voltage Input Low Voltage Min. 4.5 0 2.2 -0.5(1) Typ. 5.0 0 ____ Max. 5.5 0 6.0(2) 0.8 Unit V V V V 2721 tbl 04 ____ Capacitance(1) (TA = +25°C, f = 1.0MHz) Symbol CIN COUT Parameter Input Capacitance Output Capacitance Conditions(2) V IN = 3dV V OUT = 3dV Max. 9 10 Unit pF pF 2721 tbl 02 NOTES: 1. VIL (min.) > -1.5V for pulse width less than 10ns. 2. VTERM must not exceed Vcc + 10%. NOTES: 1. This parameter is determined by device characterization but is not production tested. 2. 3dv references the interpolated capacitance when the input and output signals switch from 0V to 3V and from 3V to 0V. DC Electrical Characteristics Over the Operating Temperature and Supply Voltage (VCC = 5V ± 10%) 71342SA Symbol |ILI| |ILO| VOL Parameter Input Leakage Current (1) 71342LA Min. ___ Test Conditions VCC = 5.5V, VIN = 0V to V CC CE = VIH, VOUT = 0V to V CC IOL = 6mA IOL = 8mA Min. ___ Max. 10 10 0.4 0.5 ___ Max. 5 5 0.4 0.5 ___ Unit µA µA V V V 2721 tbl 05 Output Leakage Current Output Low Voltage ___ ___ ___ ___ ___ ___ VOH Output High Voltage IOH = -4mA 2.4 2.4 NOTE: 1. At Vcc < 2.0V input leakages are undefined. 3 6.42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges DC Electrical Characteristics Over the Operating Temperature and Supply Voltage Range(1) (VCC = 5.0V ± 10%) 71342X20 Com'l Only Symbol ICC Parameter Dynamic Operating Current (Both Ports Active) Test Condition CE = VIL, Outputs Disabled SEM = Don't Care f = fMAX(3) CEL and C ER = VIH SEML = SEMR > VIH f = fMAX(3) Version COM'L IND COM'L IND COM'L IND COM'L IND COM'L IND SA LA SA LA SA LA SA LA SA LA SA LA SA LA SA LA SA LA SA LA Typ. (2) 170 170 ____ ____ 71342X25 Com'l & Ind Typ. (2) 160 160 160 160 25 25 25 25 95 95 95 95 1.0 0.2 1.0 0.2 95 95 95 95 Max. 280 240 310 260 80 50 100 80 180 150 210 170 15 4.0 30 10 170 120 210 190 71342X35 Com'l & Ind Typ. (2) 150 150 150 150 25 25 25 25 85 85 85 85 1.0 0.2 1.0 0.2 85 85 85 85 Max. 260 200 300 250 75 45 75 55 170 140 200 160 15 4.0 30 10 150 110 190 130 2721 tbl 06a Max. 280 240 ____ ____ Unit mA ISB1 Standby Current (Both Ports - TTL Level Inputs) 25 25 ____ ____ 80 80 ____ ____ mA ISB2 Standby Current (One Port - TTL Level Inputs) CE"A" = VIL and C E"B" = VIH Active Port Outputs Disabled, f=fMAX(3) 105 105 ____ ____ 180 150 ____ ____ mA ISB3 Full Standby Current (Both Ports CMOS Level Inputs) Both Ports C EL and CER > VCC - 0.2V, VIN > VCC - 0.2V or V IN < 0.2V SEML = SEMR > VCC - 0.2V f = 0(3) One Port C E"A" o r CE"B" > VCC - 0.2V VIN > VCC - 0.2V or V IN < 0.2V SEML = SEMR > VCC - 0.2V Active Port Outputs Disabled, f = fMAX(3) 1.0 0.2 ____ ____ 15 4.5 ____ ____ mA ISB4 Full Standby Current (One Port CMOS Level Inputs) 105 105 ____ ____ 170 130 ____ ____ mA 71342X45 Com'l Only Symbol ICC Parameter Dynamic Operating Current (Both Ports Active) Test Condition CE = VIL, Outputs Disabled SEM = Don't Care f = fMAX(3) CEL and C ER = VIH SEML = SEMR > VIH f = fMAX(3) Version COM'L IND COM'L IND COM'L IND COM'L IND COM'L IND SA LA SA LA SA LA SA LA SA LA SA LA SA LA SA LA SA LA SA LA Typ. (2) 140 140 ____ ____ 71342X55 Com'l & Ind Typ. (2) 140 140 140 140 25 25 25 25 75 75 75 75 1.0 0.2 1.0 2.0 75 75 75 75 Max. 240 200 270 220 70 40 70 50 160 130 180 150 15 4.0 30 10 150 100 170 120 71342X70 Com'l Only Typ. (2) 140 140 ____ ____ Max. 240 200 ____ ____ Max. 240 200 ____ ____ Unit mA ISB1 Standby Current (Both Ports - TTL Level Inputs) 25 25 ____ ____ 70 40 ____ ____ 25 25 ____ ____ 70 40 ____ ____ mA ISB2 Standby Current (One Port - TTL Level Inputs) CE"A" = VIL and C E"B" = VIH Active Port Outputs Disabled, f=fMAX(3) 75 75 ____ ____ 160 130 ____ ____ 75 75 ____ ____ 160 130 ____ ____ mA ISB3 Full Standby Current (Both Ports CMOS Level Inputs) Both Ports C EL and CER > VCC - 0.2V, VIN > VCC - 0.2V or V IN < 0.2V SEML = SEMR > VCC - 0.2V f = 0(3) One Port C E"A" o r CE"B" > VCC - 0.2V VIN > VCC - 0.2V or V IN < 0.2V SEML = SEMR > VCC - 0.2V Active Port Outputs Disabled, f = fMAX(3) 1.0 0.2 ____ ____ 15 4.0 ____ ____ 1.0 0.2 ____ ____ 15 4.0 ____ ____ mA ISB4 Full Standby Current (One Port CMOS Level Inputs) 75 75 ____ ____ 150 100 ____ ____ 75 75 ____ ____ 150 100 ____ ____ mA 2721 tbl 06b NOTES: 1. 'X' in part number indicates power rating (SA or LA). 2. VCC = 5V, TA = +25°C for typical, and parameters are not production tested. 3. fMAX = 1/tRC = All inputs cycling at f = 1/tRC (except Output Enable). f = 0 means no address or control lines change. Applies only to inputs at CMOS level standby ISB3. 6.42 4 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges Data Retention Characteristics Symbol VDR ICCDR tCDR(3) tR (3) (LA Version Only) VLC = 0.2V, VHC = VCC - 0.2V Parameter VCC for Data Retention Data Retention Current Chip Deselect to Data Retention Time Operation Recovery Time VCC = 2V, C E > VHC SEM > VHC VIN > VHC o r < VLC Test Condition ___ Min. 2.0 Typ.(1) Max. ___ Unit V µA ns ns 2721 tbl 07 COM'L. & IND. ___ 100 ___ 1500 ___ 0 tRC (2) ___ ___ NOTES: 1. VCC = 2V, TA = +25°C, and are not production tested. 2. tRC = Read Cycle Time. 3. This parameter is guaranteed by device characterization, but is not production tested. Data Rention Waveform DATA RETENTION MODE VCC 4.5V tCDR CE VIH VDR VDR > 2V 4.5V tR VIH 2721 drw 04 AC Test Conditions Input Pulse Levels Input Rise/Fall Times Input Timing Reference Levels Output Reference Levels Output Load GND to 3.0V 5ns 1.5V 1.5V Figures 1 and 2 2721 tbl 08 +5V 1250Ω DATAOUT 775Ω 30pF 2721 drw 05 , +5V 1250Ω DATAOUT 775Ω 5pF * , 2721 drw 06 Figure 1. AC Output Test Load Figure 2. Output Test Load (for t LZ, tHZ, t WZ, tOW) *Including scope and jig 5 6.42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges AC Electrical Characteristics Over the Operating Temperature and Supply Voltage(5) 71342X20 Com'l Only Symbol READ CYCLE tRC tAA tACE tAOE tOH tLZ tHZ tPU tPD tSOP tWDD tDDD tSAA Read Cycle Time Address Access Time Chip Enable Access Time (3) Output Enable Access Time Output Hold from Address Change Output Low-Z Time (1,2) (1,2) 71342X25 Com'l & Ind Min. Max. 71342X35 Com'l & Ind Min. Max. Unit Parameter Min. Max. 20 ____ ____ 25 ____ ____ 35 ____ ____ ns ns ns ns ns ns ns ns ns ns ns ns ns 2721 tbl 09a 20 20 15 ____ ____ 25 25 15 ____ ____ 35 35 20 ____ ____ ____ ____ ____ ____ ____ ____ 0 0 ____ 0 0 ____ 0 0 ____ Output High-Z Time 15 ____ 15 ____ 20 ____ Chip Enable to Power Up Time (2) Chip Disable to Power Down Time(2) SEM Flag Update Pulse (OE or SEM) Write Pulse to Data Delay (4) (4) 0 ____ 0 ____ 0 ____ 50 ____ 50 ____ 50 ____ 10 ____ 10 ____ 15 ____ 40 30 ____ 50 30 25 60 35 35 Write Data Valid to Read Data Delay Semaphore Address Access Time ____ ____ ____ ____ ____ ____ 71342X45 Com'l Only Symbol READ CYCLE tRC tAA tACE tAOE tOH tLZ tHZ tPU tPD tSOP tWDD tDDD tSAA Read Cycle Time Address Access Time Chip Enable Access Time (3) 71342X55 Com'l & Ind Min. Max. 71342X70 Com'l Only Min. Max. Unit Parameter Min. Max. 45 ____ ____ 55 ____ ____ 70 ____ ____ ns ns ns ns ns ns ns ns ns ns ns ns ns 2721 tbl 09b 45 45 25 ____ 55 55 30 ____ 70 70 40 ____ ____ ____ ____ Output Enable Access Time Output Hold from Address Change Output Low-Z Time(1,2) Output High-Z Time (1,2) (2) (2) ____ ____ ____ 0 5 ____ 0 5 ____ 0 5 ____ ____ ____ ____ 20 ____ 25 ____ 30 ____ Chip Enable to Power Up Time 0 ____ 0 ____ 0 ____ Chip Disable to Power Down Time 50 ____ 50 ____ 50 ____ SEM Flag Update Pulse (OE or SEM) Write Pulse to Data Delay (4) Write Data Valid to Read Data Delay Semaphore Address Access Time (4) 15 ____ 20 ____ 20 ____ 70 45 45 80 55 55 90 70 70 ____ ____ ____ ____ ____ ____ NOTES: 1. Transition is measured 0mV from Low or High-impedance voltage with the Ouput Test Load (Figure 2). 2. This parameter is guaranteed by device characterization, but is not production tested. 3. To access SRAM, CE = VIL, SEM = VIH. To access semaphore, CE = VIH, and SEM = VIL. 4. 'X' in part number indicates power rating (SA or LA). 5. Port-to-port delay through RAM cells from writing port to reading port, refer to “Timing Waveform of Write with Port-to-Port Read”. 6.42 6 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges Timing Waveform of Read Cycle No. 1, Either Side(1,2,4) tRC ADDRESS tAA tOH DATAOUT PREVIOUS DATA VALID or tSAA tOH DATA VALID 2721 drw 07 Timing Waveform of Read Cycle No. 2, Either Side(1,3) tSOP CE or SEM (5) tACE tSOP OE tLZ DATAOUT tLZ tPU ICC CURRENT ISB 50% (1) (1) tAOE(4) tHZ (2) tHZ VALID DATA (4) (2) tPD 50% 2721 drw 08 NOTES: 1. Timing depends on which signal is asserted last, OE or CE . 2. Timing depends on which signal is de-asserted first, OE or CE . 3. R/W = VIH and OE = VIL, unless otherwise noted. 4. Start of valid data depends on which timing becomes effective last; tAOE, tACE , or tAA 5. To access SRAM, CE = VIL and SEM = V IH. To access semaphore, CE = VIH and SEM = VIL. tAA is for SRAM Address Access and t SAA is for Semaphore Address Access. Timing Waveform of Write with Port-to-Port Read(2,3) tWC ADDR "A" MATCH tWP R/W "A" (1) tDW DATAIN "A" VALID tDH ADDR "B" MATCH tWDD DATAOUT "B" tDDD NOTES: 1. Write cycle parameters should be adhered to, in order to ensure proper writing. 2. CEL = CER = VIL. CE"B" = VIL. 3. Port "A" may be either left or right port. Port "B" is the opposite from port "A". VALID 2721 drw 09 7 6.42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges AC Electrical Characteristics Over the Operating Temperature Supply Voltage(5) 71342X20 Com'l Only Symbol WRITE CYCLE tWC tEW tAW tAS tWP tWR tDW tHZ tDH tWZ tOW tSWR tSPS Write Cycle Time Chip Enable to End-of-Write (3) 71342X25 Com'l & Ind Min. Max. 71342X35 Com'l & Ind Min. Max. Unit Parameter Min. Max. 20 15 15 0 15 0 15 ____ ____ 25 20 20 0 20 0 15 ____ ____ 35 30 30 0 25 0 20 ____ ____ ns ns ns ns ns ns ns ns ns ns ns ns ns 2721 tbl 10a ____ ____ ____ ____ ____ ____ Address Valid to End-of-Write Address Set-up Time Write Pulse Width Write Recovery Time Data Valid to End-of-Write Output High-Z Time (1,2) Data Hold Time (4) (1,2) ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ 15 ____ 15 ____ 20 ____ 0 ____ 0 ____ 3 ____ Write Enable to Output in High-Z Output Active from End-of-Write SEM Flag Write to Read Time SEM Flag Contention Window 15 ____ 15 ____ 20 ____ (1,2,4) 3 10 10 3 10 10 3 10 10 ____ ____ ____ ____ ____ ____ 71342X45 Com'l Only Symbol WRITE CYCLE tWC tEW tAW tAS tWP tWR tDW tHZ tDH tWZ tOW tSWR tSPS Write Cycle Time Chip Enable to End-of-Write (3) 71342X55 Com'l & Ind Min. Max. 71342X70 Com'l Only Min. Max. Unit Parameter Min. Max. 45 40 40 0 40 0 20 ____ ____ 55 50 50 0 50 0 25 ____ ____ 70 60 60 0 60 0 30 ____ ____ ns ns ns ns ns ns ns ns ns ns ns ns ns 2721 tbl 10b ____ ____ ____ ____ ____ ____ Address Valid to End-of-Write Address Set-up Time Write Pulse Width Write Recovery Time Data Valid to End-of-Write Output High-Z Time Data Hold Time (4) (1,2) (1,2) ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ ____ 20 ____ 25 ____ 30 ____ 3 ____ 3 ____ 3 ____ Write Enable to Output in High-Z Output Active from End-of-Write SEM Flag Write to Read Time SEM Flag Contention Window 20 ____ 25 ____ 30 ____ (1,2,4) 3 10 10 3 10 10 3 10 10 ____ ____ ____ ____ ____ ____ NOTES: 1. Transition is measured 0mV 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 SRAM, CE = VIL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. Either condition must be valid for the entire tEW time. 4. The specification for tDH must be met by the device supplying write data to the SRAM under all operating conditions. Although tDH and tOW values will vary over voltage and temperature, the actual tDH will always be smaller than the actual tOW. 5. 'X' in part number indicates power rating (SA or LA). 6.42 8 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges TIMING WAVEFORM OF WRITE CYCLE NO. 1, R/W CONTROLLED TIMING(1,5,8) tWC ADDRESS tAS (6) OE tAW CE or SEM (9) tWR (3) tWP (2) R/W tLZ DATAOUT tWZ (7) (4) tHZ (7) tOW (4) tHZ (7) tDW DATAIN tDH 2721 drw 10 Timing Waveform of Write Cycle No. 2, CE Controlled Timing(1, 5) tWC ADDRESS tAW CE or SEM (9) (6) (2) (3) tAS R/W tEW tWR tDW DATAIN tDH 2721 drw 11 NOTES: 1. R/W or CE must be HIGH during all address transitions. 2. A write occurs during the overlap (tEW or tWP) of either CE or SEM = VIL and R/W = VIL. 3. tWR is measured from the earlier of CE 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 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 (CE or R/W) is asserted last. 7. This parameter is guaranteed by device characterization, but is not production tested. Transition is measured 0mV from steady state with the Output Test Load (Figure 2). 8. If OE is LOW during a R/W controlled write cycle, the write pulse width must be the larger of tWP or (tWZ + tDW) to allow the I/O drivers to turn off 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 tWP . 9. To access SRAM, CE =V IL and SEM = VIH. To access semaphore, CE = VIH and SEM = VIL. Either condition must be valid for the entire tEW time. 9 6.42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges Timing Waveform of Semaphore Read After Write Timing, Either Side(1) tSAA A0 - A2 VALID ADDRESS tAW SEM tEW tDW DATA0 tAS R/W tSWRD OE Write Cycle NOTE: 1. CE = VIH for the duration of the above timing (both write and read cycle). tOH VALID ADDRESS tACE tWR tSOP DATAOUT VALID DATAIN VALID tWP tDH tAOE tSOP Test Cycle (Read Cycle) 2721 drw 12 Timing Waveform of Semaphore Condition(1,3,4) A0"A" - A2"A" MATCH SIDE(2) "A" R/W"A" SEM"A" tSPS A0"B" - A2"B" MATCH SIDE(2) "B" R/W"B" SEM"B" 2721 drw 13 NOTES: 1. D0R = D0L = VIL, CER = CE L = VIH, Semaphore Flag is released from both sides (reads as ones from both sides) at cycle start. 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 the point where R/W "A" or SEM "A" goes HIGH until R/W " B" or SEM " B" goes HIGH. 4. If tSPS is violated, the semaphore will fall positively to one side or the other, but there is no guarantee which side will obtain the flag. 610 .42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges FUNCTIONAL DESCRIPTION The IDT71342 is an extremely fast Dual-Port 4K x 8 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 designer’s software. As an example, the semaphore 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 CMOS Static RAMs 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 SRAM. These devices have an automatic power-down feature controlled by CE, the Dual-Port SRAM 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 I where CE and SEM are both HIGH. Systems which can best use the IDT71342 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 IDT71342’s hardware semaphores, which provide a lockout mechanism without requiring complex programming. Software handshaking between processors offers the maximum in system flexibility by permitting shared resources to be allocated in varying configurations. The IDT71342 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 a 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 had set the latch first, has the token and is using the shared resource. The left processor can then either repeatedly request that semaphore’s 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 requested 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 IDT71342 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 the address pins A0–A2. When accessing the semaphores, none of the other address pins has any effect. When writing to a semaphore, only data pin D0 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 (see Truth Table II). 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 communications. (A thorough discussion 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 side’s 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 of WRITE/READ must be used by the semaphore 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 a one, a fact which the processor will verify by the subsequent read (see Truth Table II). As an example, assume a processor writes a zero in 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 a 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 3. Two semaphore 611 .42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges request latches feed into a semaphore 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 one is written to the same semaphore request latch. Should the other side’s semaphore request latch have been written to a zero in the meantime, the semaphore 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 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. Code integrity is of the utmost importance when semaphores are used instead of slower, more restrictive hardware intensive schemes. 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 Truth Table I — Non-Contention Read/Write Control(2) Left or Right Port(1) R/W X H X ↑ H L X CE H H X H L L L SEM H L X L H H L OE X L H X L X X D0-7 Z DATAOUT Z DATAIN DATAOUT DATAIN ____ Function Port Disabled and in Power Down Mode Data in Semaphore Flag Output on Port Output Disabled Port Data Bit D0 Written Into Semaphore Flag Data in Memory Output on Port Data on Port Written Into Memory Not Allowed 2721 tbl 11 NOTE: 1. AOL = A11L ¹ A0R - A11R. 2. "H" = VIH, "L" = VIL, "X" = Don’t Care, "Z" = High-Impedance. Truth Table II — Example Semaphore Procurement Sequence(1,2,3) Functions No Action Left Port Writes "0" to Semaphore Right Port Writes "0" to Semaphore Left Port Writes "1" to Semaphore Left Port Writes "0" to Semaphore Right Port Writes "1" to Semaphore Left Port Writes "1" to Semaphore Right Port Writes "0" to Semaphore Right Port Writes "1" to Semaphore Left Port Writes "0" to Semaphore Left Port Writes "1" to Semaphore D0 - D15 Left 1 0 0 1 1 0 1 1 1 0 1 D0 - D15 Right 1 1 1 0 0 1 1 0 1 1 1 Semaphore free Left port has semaphore token No change. Right side has no write access to semaphore Right port obtains semaphore token No change. Left port has no write access to semaphore Left port obtains semaphore token Semaphore free Right port has semaphore token Semaphore free Left port has semaphore token Semaphore free 2721 tbl 12 Status NOTE: 1. This table denotes a sequence of events for only one of the eight semaphores on the IDT71342. 2. There are eight semaphore flags written to via I/O0 and read from all I/O's. These eight semaphores are addressed by A0-A2. 3. CE = VIH, SEM = VIL to access the semaphores. Refer to the semaphore Read/Write Control Truth Table. 612 .42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges 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 Semaphores–Some examples Perhaps the simplest application of semaphores is their application as resource markers for the IDT71342’s Dual-Port RAM. Say the 4K x 8 RAM was to be divided into two 2K x 8 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 the memory. To take a resource, in this example the lower 2K of Dual-Port RAM, the processor on the left port could write and then read a zero into Semaphore 0. If this task were successfully completed (a zero was read back rather than a one), the left processor would assume control of the lower 2K. Meanwhile, the right processor would attempt to perform the same function. Since this 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 2K 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 2K blocks of Dual-Port RAM with each other. The blocks do not have to by 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 had 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 processors can access their assigned RAM segments at full speed. Another application is in the area of complex data structures. 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. L PORT SEMAPHORE REQUEST FLIP FLOP D0 WRITE D Q R PORT SEMAPHORE REQUEST FLIP FLOP Q D D0 WRITE SEMAPHORE READ Figure 3. IDT71342 Semaphore Logic SEMAPHORE READ 2721 drw 14 613 .42 IDT71342SA/LA High-Speed 4K x 8 Dual-Port Static RAM with Semaphore Industrial and Commercial Temperature Ranges Ordering Information IDT XXXX Device Type A Power 999 Speed A Package A Process/ Temperature Range Blank I J PF 20 25 35 45 55 70 SA LA 71342 Commercial (0°C to +70°C) Industrial (-40°C to +85°C) 52-pin PLCC (J52-1) 64-pin TQFP (PN64-1) Commercial Only Commercial & Industrial Commercial & Industrial Commercial Only Commercial & Industrial Commercial Only Standard Power Low Power 32K (4K x 8-Bit) Dual-Port RAM w/ Semaphore 2721 drw 15 Speed in nanoseconds Datasheet Document History 1/12/99: Initiated datasheet document history Converted to new format Cosmetic and typographical corrections Added additional notes to pin configurations Changed drawing format Added Industrial Temperature Ranges and removed corresponding notes Replaced IDT logo Page 1 Made corrections to drawing Page 3 Increased storage temperature parameters Clarified TA parameter Page 4 DC Electrical parameters–changed wording from "open" to "disabled" Changed ±500mV to 0mV in notes Pages 1 and 2 Moved "Description" to page 2 and adjusted page layouts Page 1 Added "(LA only)" to paragraph Page 2 Fixed J52 package description in notes Page 8 Replaced bottom table with correct 10b table 6/9/99: 10/1/99: 11/10/99: 12/22/99: 6/26/00: 1/12/00: CORPORATE HEADQUARTERS 6024 Silver Creek Valley Road San Jose, CA 95138 for SALES: 800-345-7015 or 408-284-8200 fax: 408-284-2775 www.idt.com 614 .42 for Tech Support: 408-284-2794 DualPortHelp@idt.com The IDT logo is a registered trademark of Integrated Device Technology, Inc.