ADVANCED INFORMATION IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 Integrated Device Technology, Inc. internal pointers that load and empty data on a first-in/first-out basis. The device uses Full and Empty flags to prevent data overflow and underflow and expansion logic to allow for unlimited expansion capability in both word size and depth. Data is toggled in and out of the device through the use of the Write (W) and Read (R) pins. The device's 9-bit width provides a bit for a control or parity at the user’s option. It also features a Retransmit (RT) capability that allows the read pointer to be reset to its initial position when RT is pulsed LOW. A Half-Full Flag is available in the single device and width expansion modes. The IDT7208 is fabricated using IDT’s high-speed CMOS technology. It is designed for applications requiring asynchronous and simultaneous read/writes in multiprocessing, rate buffering, and other applications. FEATURES: • 65536 x 9 storage capacity • High-speed: 15ns access time • Low power consumption — Active: 660mW (max.) — Power-down: 44mW (max.) • Asynchronous and simultaneous read and write • Fully expandable in both word depth and width • Pin and functionally compatible with IDT720x family • Status Flags: Empty, Half-Full, Full • Retransmit capability • High-performance CMOS technology • Industrial temperature range (-40oC to +85oC) is available, tested to military electrical specifications DESCRIPTION: The IDT7208 is a monolithic dual-port memory buffer with FUNCTIONAL BLOCK DIAGRAM DATA INPUTS (D 0 –D 8) WRITE CONTROL W • RAM ARRAY 65,536 x 9 WRITE POINTER THREESTATE BUFFERS READ CONTROL R • • • RS DATA OUTPUTS (Q 0 –Q 8 ) • • • • FLAG LOGIC EXPANSION LOGIC XI READ POINTER EF FF RESET LOGIC FL/RT XO/HF 3274 drw 01 The IDT logo is a registered trademark of Integrated Device Technology, Inc. COMMERCIAL TEMPERATURE RANGES 1996 Integrated Device Technology, Inc. DECEMBER 1996 For latest information contact IDT's web site at www.idt.com or fax-on-demand at 408-492-8391. 5.06 DSC-3274/1 1 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 Q0 Q1 Q2 Q3 Q8 GND XI FL/RT FF RS Q0 Q1 NC Q2 EF XO/HF Q7 Q6 Q5 Q4 R W 29 28 27 26 25 24 23 22 21 1 5 6 7 8 9 10 11 12 13 32 31 30 3 2 4 D2 D1 D0 J32-1 D6 D7 NC FL/RT RS EF / XO HF Q7 Q6 Q4 Q5 FF P28-1 INDEX Vcc D4 D5 D6 D7 R XI 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 15 16 17 18 19 20 D8 D3 D2 D1 D0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Q3 Q8 GND NC W D3 D8 PIN CONFIGURATIONS NC Vcc D4 D5 COMMERCIAL TEMPERATURE RANGES 3274 drw 03 3274 drw 02 PLCC TOP VIEW DIP TOP VIEW ABSOLUTE MAXIMUM RATINGS(1) Symbol VTERM Rating Terminal Voltage with Respect to GND Commercial Unit –0.5 to + 7.0 V 0 to +70 °C Temperature Under Bias –55 to +125 °C Storage Temperature –55 to + 125 °C 50 mA TA Operating Temperature TBIAS TSTG IOUT DC Output Current RECOMMENDED DC OPERATING CONDITIONS Symbol NOTE: 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. Parameter VCCC Commercial Supply Voltage GND Supply Voltage Min. Typ. Max. Unit 4.5 5.0 5.5 V 0 0 0 V (1) VIH Input High Voltage Commercial 2.0 — — V VIL(1) Input Low Voltage Commercial — — 0.8 V NOTE: 1. 1.5V undershoots are allowed for 10ns once per cycle. DC ELECTRICAL CHARACTERISTICS FOR THE 7208 (Commercial: VCC = 5.0V±10%, TA = 0°C to +70°C) IDT7208 Commercial tA = 20, 25, 35 ns Symbol Parameter Min. Typ. Max. Unit ILI(1) Input Leakage Current (Any Input) –1 — 1 µA ILO(2) Output Leakage Current –10 — 10 µA VOH Output Logic “1” Voltage IOH = –2mA 2.4 — — V VOL Output Logic “0” Voltage IOL = 8mA — — 0.4 V ICC1(3) Active Power Supply Current ICC2(3) Standby Current (R=W=RS=FL/RT=VIH) ICC3(L)(3) Power Down Current (All Input = VCC - 0.2V) — (4) — 120 mA — — 12 mA — — 8 mA NOTES: 1. Measurements with 0.4 ≤ VIN ≤ VCC. 2. R ≥ VIH, 0.4 ≤ VOUT ≤ VCC. 3. ICC measurements are made with outputs open (only capacitive loading). 4. Tested at f = 20MHz. 5.06 2 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES AC ELECTRICAL CHARACTERISTICS(1) (Commercial: VCC = 5V ± 10%, TA = 0°C to +70°C) Commercial 7208L20 Symbol Parameters fS tRC tA tRR 7208L25 Min. Max. Shift Frequency — Read Cycle Time 30 Access Time — Read Recovery Time 10 tRPW Read Pulse Width(2) tRLZ Read LOW to Data Bus LOW(3) (3, 4) 7208L35 Min. Max. Min. Max. Unit 33.3 — — 35 28.5 — 22.2 MHz — 45 — ns 20 — — 10 25 — 35 ns — 10 — ns 20 — 5 — 25 — 35 — ns 5 — 5 — ns ns tWLZ Write HIGH to Data Bus Low-Z 5 — 5 — 10 — tDV Data Valid from Read HIGH 5 — 5 — 5 — ns tRHZ Read HIGH to Data Bus High-Z(3) — 15 — 18 — 20 ns tWC Write Cycle Time 30 — 35 — 45 — ns tWPW Write Pulse Width(2) 20 — 25 — 35 — ns tWR Write Recovery Time 10 — 10 — 10 — ns tDS Data Set-up Time 12 — 15 — 18 — ns tDH Data Hold Time 0 — 0 — 0 — ns tRSC Reset Cycle Time 30 — 35 — 45 — ns tRS Reset Pulse Width(2) 20 — 25 — 35 — ns tRSS Reset Set-up Time(3) 20 — 25 — 35 — ns tRTR Reset Recovery Time 10 — 10 — 10 — ns tRTC Retransmit Cycle Time 30 — 35 — 45 — ns tRT Retransmit Pulse Width(2) 20 — 25 — 35 — ns tRTS Retransmit Set-up Time(3) 20 — 25 — 35 — ns tRSR Retransmit Recovery Time 10 — 10 — 10 — ns tEFL Reset to EF LOW — 30 — 35 — 45 ns tHFH, tFFH Reset to HF and FF HIGH — 30 — 35 — 45 ns tRTF Retransmit LOW to Flags Valid — 30 — 35 — 45 ns tREF Read LOW to EF LOW — 20 — 25 — 30 ns tRFF Read HIGH to FF HIGH — 20 — 25 — 30 ns tRPE Read Pulse Width after EF HIGH 20 — 25 — 35 — ns tWEF Write HIGH to EF HIGH — 20 — 25 — 30 ns tWFF Write LOW to FF LOW — 20 — 25 — 30 ns tWHF Write LOW to HF Flag LOW — 30 — 35 — 45 ns tRHF Read HIGH to HF Flag HIGH — 30 — 35 — 45 ns tWPF Write Pulse Width after FF HIGH 20 — 25 — 35 — ns tXOL Read/Write LOW to XO LOW — 20 — 25 — 35 ns tXOH Read/Write HIGH to XO HIGH tXI XI tXIR tXIS — 20 — 25 — 35 ns Pulse Width(2) 20 — 25 — 35 — ns XI Recovery Time 10 — 10 — 10 — ns XI Set-up Time 10 — 10 — 15 — ns NOTES: 1. 2. 3. 4. Timings referenced as in AC Test Conditions. Pulse widths less than minimum are not allowed. Values guaranteed by design, not currently tested. Only applies to read data flow-through mode. 5.06 3 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES AC TEST CONDITIONS Input Pulse Levels Input Rise/Fall Times Input Timing Reference Levels Output Reference Levels Output Load 5V GND to 3.0V 5ns 1.5V 1.5V See Figure 1 1.1KΩ D.U.T. 680Ω 30pF* CAPACITANCE(1) (TA = +25°C, f = 1.0 MHz) Symbol Parameter Condition Max. Unit Input Capacitance VIN = 0V 10 pF Output Capacitance VOUT = 0V 10 pF CIN(1) (1,2) COUT OR EQUIVALENT CIRCUIT 3274 drw 04 Figure 1. Output Load NOTES: 1. This parameter is sampled and not 100% tested. 2. With output deselected. *Includes jig and scope capacitances. SIGNAL DESCRIPTIONS Inputs: DATA IN (D0–D8) — Data inputs for 9-bit wide data. Controls: RESET (RS) — Reset is accomplished whenever the Reset (RS) input is taken to a LOW state. During reset, both internal read and write pointers are set to the first location. A reset is required after power-up before a write operation can take place. Both the Read Enable (R) and Write Enable (W) inputs must be in the HIGH state during the window shown in Figure 2 (i.e. tRSS before the rising edge of RS) and should not change until tRSR after the rising edge of RS. WRITE ENABLE (W) — A write cycle is initiated on the falling edge of this input if the Full Flag (FF) is not set. Data set-up and hold times must be adhered-to, with respect to the rising edge of the Write Enable (W). Data is stored in the RAM array sequentially and independently of any on-going read operation. After half of the memory is filled, and at the falling edge of the next write operation, the Half-Full Flag (HF) will be set to LOW, and will remain set until the difference between the write pointer and read pointer is less-than or equal to one-half of the total memory of the device. The Half-Full Flag (HF) is reset by the rising edge of the read operation. To prevent data overflow, the Full Flag (FF) will go LOW on the falling edge of the last write signal, which inhibits further write operations. Upon the completion of a valid read operation, the Full Flag (FF) will go HIGH after tRFF, allowing a new valid write to begin. When the FIFO is full, the internal write pointer is blocked from W, so external changes in W will not affect the FIFO when it is full. READ ENABLE (R) — A read cycle is initiated on the falling edge of the Read Enable (R), provided the Empty Flag (EF) is not set. The data is accessed on a First-In/First-Out basis, independent of any ongoing write operations. After Read Enable (R) goes HIGH, the Data Outputs (Q0 through Q8) will return to a high-impedance condition until the next Read operation. When all the data has been read from the FIFO, the Empty Flag (EF) will go LOW, allowing the “final” read cycle but inhibiting further read operations, with the data outputs remaining in a highimpedance state. Once a valid write operation has been accomplished, the Empty Flag (EF) will go HIGH after tWEF and a valid Read can then begin. When the FIFO is empty, the internal read pointer is blocked from R so external changes will not affect the FIFO when it is empty. FIRST LOAD/RETRANSMIT (FL/RT) — This is a dualpurpose input. In the Depth Expansion Mode, this pin is grounded to indicate that it is the first device loaded (see Operating Modes). The Single Device Mode is initiated by grounding the Expansion In (XI). The IDT7208 can be made to retransmit data when the Retransmit Enable Control (RT) input is pulsed LOW. A retransmit operation will set the internal read pointer to the first location and will not affect the write pointer. The status of the Flags will change depending on the relative locations of the read and write pointers. Read Enable (R) and Write Enable (W) must be in the HIGH state during retransmit. This feature is useful when less than 65,536 writes are performed between resets. The retransmit feature is not compatible with the Depth Expansion Mode. EXPANSION IN (XI) — This input is a dual-purpose pin. Expansion In (XI) is grounded to indicate an operation in the single device mode. Expansion In (XI) is connected to Expansion Out (XO) of the previous device in the Depth Expansion or Daisy-Chain Mode. 5.06 4 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES and will remain set until the difference between the write pointer and read pointer is less than or equal to one half of the total memory of the device. The Half-Full Flag (HF) is then reset by the rising edge of the read operation. In the Depth Expansion Mode, Expansion In (XI) is connected to Expansion Out (XO) of the previous device. This output acts as a signal to the next device in the Daisy Chain by providing a pulse to the next device when the previous device reaches the last location of memory. There will be an XO pulse when the Write pointer reaches the last location of memory, and an additional XO pulse when the Read pointer reaches the last location of memory. Outputs: FULL FLAG (FF) — The Full Flag (FF) will go LOW, inhibiting further write operations, when the device is full. If the read pointer is not moved after Reset (RS), the Full Flag (FF) will go LOW after 65,536 writes. EMPTY FLAG (EF) — The Empty Flag (EF) will go LOW, inhibiting further read operations, when the read pointer is equal to the write pointer, indicating that the device is empty. EXPANSION OUT/HALF-FULL FLAG (XO/HF) — This is a dual-purpose output. In the single device mode, when Expansion In (XI) is grounded, this output acts as an indication of a halffull memory. After half of the memory is filled, and at the falling edge of the next write operation, the Half-Full Flag (HF) will be set to LOW DATA OUTPUTS (Q0-Q8) — Q0-Q8 are data outputs for 9bit wide data. These outputs are in a high-impedance condition whenever Read (R) is in a HIGH state. t RSC t RS RS t RSS t RSR W t RSS R t EFL EF t HFH , t FFH , HF FF 3274 drw 05 NOTE: 1. W and R = VIH around the rising edge of RS. Figure 2. Reset t RC t RPW t RR tA tA R t DV t RLZ DATA Q 0 –Q 8 OUT VALID t RHZ DATA OUT VALID t WC t WPW t WR W t DS D 0 –D 8 DATA t DH IN DATA VALID IN VALID 3274 drw 06 Figure 3. Asynchronous Write and Read Operation 5.06 5 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES IGNORED WRITE LAST WRITE FIRST READ R W t WFF t RFF FF 3274 drw 07 Figure 4. Full FlagTiming From Last Write to First Read IGNORED READ LAST READ FIRST WRITE W R t REF t WEF EF tA DATAOUT VALID 3274 drw 08 Figure 5. Empty Flag Timing From Last Read to First Write t RTC t RT RT t RTS t RTR , W R RTF , , FLAG VALID HF EF FF 3274 drw 09 NOTE: 1. EF, FF and HF may change status during Retransmit, but flags will be valid at tRTC. Figure 6. Retransmit 5.06 6 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES W t WEF EF t RPE R 3274 drw 10 Figure 7. Minimum Timing for an Empty Flag Coincident Read Pulse. R t RFF FF t WPF W 3274 drw 11 Figure 8. Minimum Timing for an Full Flag Coincident Write Pulse. W t RHF R t WHF HF HALF-FULL OR LESS MORE THAN HALF-FULL HALF-FULL OR LESS 3274 drw 12 Figure 9. Half-Full Flag Timing W WRITE TO LAST PHYSICAL LOCATION READ FROM LAST PHYSICAL LOCATION R t XOL t XOH t XOL t XOH XO 3274 drw 13 Figure 10. Expansion Out 5.06 7 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 t XI COMMERCIAL TEMPERATURE RANGES t XIR XI t XIS W WRITE TO FIRST PHYSICAL LOCATION t XIS READ FROM FIRST PHYSICAL LOCATION R 3274 drw 14 Figure 11. Expansion In OPERATING MODES: Care must be taken to assure that the appropriate flag is monitored by each system (i.e. FF is monitored on the device where W is used; EF is monitored on the device where R is used). tus flags (EF, FF and HF) can be detected from any one device. Figure 13 demonstrates an 18-bit word width by using two IDT7208s. Any word width can be attained by adding additional IDT7208s (Figure 13). Single Device Mode A single IDT7208 may be used when the application requirements are for 65,536 words or less. The IDT7208 is in a Single Device Configuration when the Expansion In (XI) control input is grounded (see Figure 12). Bidirectional Operation Applications which require data buffering between two systems (each system capable of Read and Write operations) can be achieved by pairing IDT7208s as shown in Figure 16. Both Depth Expansion and Width Expansion may be used in this mode. Depth Expansion The IDT7208 can easily be adapted to applications when the requirements are for greater than 65,536 words. Figure 14 demonstrates Depth Expansion using three IDT7208s. Any depth can be attained by adding additional IDT7208s. The IDT7208 operates in the Depth Expansion mode when the following conditions are met: 1. The first device must be designated by grounding the First Load (FL) control input. 2. All other devices must have FL in the HIGH state. 3. The Expansion Out (XO) pin of each device must be tied to the Expansion In (XI) pin of the next device. See Figure 14. 4. External logic is needed to generate a composite Full Flag (FF) and Empty Flag (EF). This requires the ORing of all EFs and ORing of all FFs (i.e. all must be set to generate the correct composite FF or EF). See Figure 14. 5. The Retransmit (RT) function and Half-Full Flag (HF) are not available in the Depth Expansion Mode. USAGE MODES: Width Expansion Word width may be increased simply by connecting the corresponding input control signals of multiple devices. Sta- Data Flow-Through Two types of flow-through modes are permitted, a read flow-through and write flow-through mode. For the read flowthrough mode (Figure 17), the FIFO permits a reading of a single word after writing one word of data into an empty FIFO. The data is enabled on the bus in (tWEF + tA) ns after the rising edge of W, called the first write edge, and it remains on the bus until the R line is raised from LOW-to-HIGH, after which the bus would go into a three-state mode after tRHZ ns. The EF line would have a pulse showing temporary deassertion and then would be asserted. In the write flow-through mode (Figure 18), the FIFO permits the writing of a single word of data immediately after reading one word of data from a full FIFO. The R line causes the FF to be deasserted but the W line being LOW causes it to be asserted again in anticipation of a new data word. On the rising edge of W, the new word is loaded in the FIFO. The W line must be toggled when FF is not asserted to write new data in the FIFO and to increment the write pointer. Compound Expansion The two expansion techniques described above can be applied together in a straightforward manner to achieve large FIFO arrays (see Figure 15). 5.06 8 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES (HALF–FULL FLAG) (HF) WRITE (W) READ ( R) 9 IDT 7208 DATA IN (D) FULL FLAG ( FF) 9 DATA OUT (Q) EMPTY FLAG (EF) RETRANSMIT (RT) RESET (RS) EXPANSION IN ( XI) 3274 drw 15 Figure 12. Block Diagram of 65,536 x 9 FIFO Used in Single Device Mode HF 18 HF 9 9 DATA IN (D) WRITE (W) IDT 7208 READ (R) IDT 7208 FULL FLAG ( FF) EMPTY FLAG (EF) RESET (RS) RETRANSMIT (RT) 9 9 XI XI 18 DATA OUT (Q) 3274 drw 16 NOTE: 1. Flag detection is accomplished by monitoring the FF, Do not connect any output signals together. EF and HF signals on either (any) device used in the width expansion configuration. Figure 13. Block Diagram of 65,536 x 18 FIFO Memory Used in Width Expansion Mode 5.06 9 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES TRUTH TABLES TABLE I – RESET AND RETRANSMIT SINGLE DEVICE CONFIGURATION/WIDTH EXPANSION MODE Inputs Mode Reset Internal Status Outputs RS RT XI Read Pointer Write Pointer EF FF HF 0 X 0 Location Zero Location Zero 0 1 1 Retransmit 1 0 0 Location Zero Unchanged X X X Read/Write 1 1 0 Increment (1) Increment (1) X X X NOTE: 1. Pointer will Increment if flag is HIGH. 7208 tbl 07 TABLE II – RESET AND FIRST LOAD DEPTH EXPANSION/COMPOUND EXPANSION MODE Inputs Mode Internal Status Outputs RS FL XI Read Pointer Write Pointer EF FF Reset First Device 0 0 (1) Location Zero Location Zero 0 1 Reset all Other Devices 0 1 (1) Location Zero Location Zero 0 1 Read/Write 1 X (1) X X X X 7208 tbl 08 NOTES: 1. XI is connected to XO of previous device. See Figure 14. 2. RS = Reset Input, FL/RT = First Load/Retransmit, EF = Empty Flag Output, FF = Full Flag Output, XI = Expansion Input, HF = Half-Full Flag Output XO W FF D 9 IDT 7208 R EF 9 9 Q FL VCC XI XO FF FULL 9 IDT 7208 EF EMPTY FL XI XO FF 9 IDT 7208 EF RS FL XI 3274 drw 17 Figure 14. Block Diagram of 196,608 x 9 FIFO Memory (Depth Expansion) 5.06 10 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES Q 0 –Q 8 Q 9 –Q 17 Q (N-8) -Q N Q (N-8) -Q N ••• Q 0 –Q 8 Q 9 –Q 17 IDT7208 DEPTH EXPANSION BLOCK IDT7208 DEPTH EXPANSION BLOCK , IDT7208 DEPTH EXPANSION BLOCK , ••• R W RS D 0 -D 8 D 9 -D 17 D (N-8) -D N D 0 –D N ••• D 9 -D N NOTES: 1. For depth expansion block see section on Depth Expansion and Figure 14. 2. For Flag detection see section on Width Expansion and Figure 13. D 18 -D N D (N-8) -D N 3274 drw 18 Figure 15. Compound FIFO Expansion WA FF A IDT 7208 IDT 7201A D A 0-8 RB EF B HF B Q B 0-8 SYSTEM A SYSTEM B Q A 0-8 RA D B 0-8 IDT 7208 WB HF A FF B EF A 3274 drw 19 Figure 16. Bidirectional FIFO Operation DATA IN W t RPE R EF t WEF t REF tA t WLZ DATA OUT DATA VALID OUT 3274 drw 20 Figure 17. Read Data Flow-Through Mode 5.06 11 IDT7208 CMOS ASYNCHRONOUS FIFO 65,536 x 9 COMMERCIAL TEMPERATURE RANGES R t WPF W t RFF FF t WFF DATA DATA IN t DATA IN DH VALID t DS A DATA OUT t OUT VALID 3274 drw 21 Figure 18. Write Data Flow-Through Mode ORDERING INFORMATION IDT XXXX X XX X X Device Type Power Speed Package Process/ Temperature Range 5.06 Blank Commercial (0°C to +70°C) P J Plastic DIP Plastic Leaded Chip Carrier 20 25 35 Commercial Only Commercial Only Commercial Only L Low Power 7208 65,536 x 9 FIFO Access Time (tA) Speed in ns 3274 drw 22 12