CY7C4255 CY7C4265 8K/16K x 18 Deep Sync FIFOs Features • Pb-Free Packages Available Functional Description • High-speed, low-power, first-in first-out (FIFO) memories • 8K x 18 (CY7C4255) • 16K x 18 (CY7C4265) • 0.5 micron CMOS for optimum speed/power • High-speed 100-MHz operation (10-ns read/write cycle times) • Low power — ICC = 45 mA • Fully asynchronous and simultaneous read and write operation • Empty, Full, Half Full, and programmable Almost Empty and Almost Full status flags • TTL compatible • Retransmit function • Output Enable (OE) pins • Independent read and write enable pins • Center power and ground pins for reduced noise • Supports free-running 50% duty cycle clock inputs The CY7C4255/65 are high-speed, low-power, first-in first-out (FIFO) memories with clocked read and write interfaces. All are 18 bits wide and are pin/functionally compatible to the CY7C42X5 Synchronous FIFO family. The CY7C4255/65 can be cascaded to increase FIFO depth. Programmable features include Almost Full/Almost Empty flags. These FIFOs provide solutions for a wide variety of data buffering needs, including high-speed data acquisition, multiprocessor interfaces, and communications buffering. These FIFOs have 18-bit input and output ports that are controlled by separate clock and enable signals. The input port is controlled by a Free-Running Clock (WCLK) and a Write Enable pin (WEN). When WEN is asserted, data is written into the FIFO on the rising edge of the WCLK signal. While WEN is held active, data is continually written into the FIFO on each cycle. The output port is controlled in a similar manner by a free-running Read Clock (RCLK) and a Read Enable pin (REN). In addition, the CY7C4255/65 have an Output Enable pin (OE). The read and write clocks may be tied together for single-clock operation or the two clocks may be run independently for asynchronous read/write applications. Clock frequencies up to 100 MHz are achievable. Retransmit and Synchronous Almost Full/Almost Empty flag features are available on these devices. • Width Expansion Capability • Depth Expansion Capability • 64-pin TQFP and 64-pin STQFP • Pin-compatible density upgrade to CY7C42X5 family • Pin-compatible density upgrade to IDT72205/15/25/35/45 Depth expansion is possible using the Cascade Input (WXI, RXI), Cascade Output (WXO, RXO), and First Load (FL) pins. The WXO and RXO pins are connected to the WXI and RXI pins of the next device, and the WXO and RXO pins of the last device should be connected to the WXI and RXI pins of the first device. The FL pin of the first device is tied to VSS and the FL pin of all the remaining devices should be tied to VCC. D0–17 Logic Block Diagram INPUT REGISTER WCLK WEN FLAG PROGRAM REGISTER WRITE CONTROL FLAG LOGIC RAM ARRAY 8K x 18 16K x 18 WRITE POINTER RS FL/RT WXI WXO/HF RXI RXO FF EF PAE PAF SMODE READ POINTER RESET LOGIC THREE–STATE OUTPUT REGISTER EXPANSION LOGIC Cypress Semiconductor Corporation Document #: 38-06004 Rev. *C Q0–17 • READ CONTROL OE 3901 North First Street RCLK • REN San Jose, CA 95134 • 408-943-2600 Revised August 2, 2005 CY7C4255 CY7C4265 Pin Configurations REN LD OE RS VCC GND EF Q17 Q16 GND Q15 VCC/SMODE Functional Description (continued) The CY7C4255/65 provides five status pins. These pins are decoded to determine one of five states: Empty, Almost Empty, Half Full, Almost Full, and Full. The Half Full flag shares the WXO pin. This flag is valid in the stand-alone and width-expansion configurations. In the depth expansion, this pin provides the expansion out (WXO) information that is used to signal the next FIFO when it will be activated. 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 Q14 Q13 GND Q12 Q11 VCC Q10 Q9 GND Q8 Q7 Q6 Q5 GND Q4 VCC Q3 Q0 Q1 GND Q2 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 CY7C4255 CY7C4265 PAE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 FL/RT WCLK WEN WXI VCC PAF RXI FF WXO/HF RXO D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 64 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 D16 D17 GND RCLK TQFP/STQFP Top View The Empty and Full flags are synchronous, i.e., they change state relative to either the Read Clock (RCLK) or the Write Clock (WCLK). When entering or exiting the Empty states, the flag is updated exclusively by the RCLK. The flag denoting Full states is updated exclusively by WCLK. The synchronous flag architecture guarantees that the flags will remain valid from one clock cycle to the next. The Almost Empty/Almost Full flags become synchronous if the VCC/SMODE is tied to VSS. All configurations are fabricated using an advanced 0.5µ CMOS technology. Input ESD protection is greater than 2001V, and latch-up is prevented by the use of guard rings. Selection Guide Maximum Frequency (MHz) 7C4255/65-10 7C4255/65-15 7C4255/65-25 7C4255/65-35 100 66.7 40 28.6 Maximum Access Time (ns) 8 10 15 20 Minimum Cycle Time (ns) 10 15 25 35 Minimum Data or Enable Set-Up (ns) Minimum Data or Enable Hold (ns) Maximum Flag Delay (ns) Active Power Supply Current (ICC1) (mA) 3 4 6 7 0.5 1 1 2 8 10 15 20 Commercial 45 45 45 45 Industrial 50 50 50 50 CY7C4255 CY7C4265 Density 8K x 18 16K x18 Package 64-pin TQFP, STQFP 64-pin TQFP, STQFP Document #: 38-06004 Rev. *C Page 2 of 22 CY7C4255 CY7C4265 Pin Descriptions Signal Name Description I/O Function D0 –17 Data Inputs I Q0–17 Data Outputs O Data outputs for an 18-bit bus. WEN Write Enable I Enables the WCLK input. REN Read Enable I Enables the RCLK input. WCLK Write Clock I The rising edge clocks data into the FIFO when WEN is LOW and the FIFO is not Full. When LD is asserted, WCLK writes data into the programmable flag-offset register. RCLK Read Clock I The rising edge clocks data out of the FIFO when REN is LOW and the FIFO is not Empty. When LD is asserted, RCLK reads data out of the programmable flag-offset register. WXO/HF Write Expansion Out/Half Full Flag O Dual-Mode Pin: Single device or width expansion – Half Full status flag. Cascaded – Write Expansion Out signal, connected to WXI of next device. EF Empty Flag O When EF is LOW, the FIFO is empty. EF is synchronized to RCLK. FF Full Flag O When FF is LOW, the FIFO is full. FF is synchronized to WCLK. PAE Programmable Almost Empty O When PAE is LOW, the FIFO is almost empty based on the almost-empty offset value programmed into the FIFO. PAE is asynchronous when VCC/SMODE is tied to VCC; it is synchronized to RCLK when VCC/SMODE is tied to VSS. PAF Programmable Almost Full O When PAF is LOW, the FIFO is almost full based on the almost full offset value programmed into the FIFO. PAF is asynchronous when VCC/SMODE is tied to VCC; it is synchronized to WCLK when VCC/SMODE is tied to VSS. LD Load I When LD is LOW, D0–17 (Q0–17) are written (read) into (from) the programmable-flag-offset register. FL/RT First Load/ Retransmit I Dual-Mode Pin: Cascaded – The first device in the daisy chain will have FL tied to VSS; all other devices will have FL tied to VCC. In standard mode or width expansion, FL is tied to VSS on all devices. Not Cascaded – Tied to VSS. Retransmit function is also available in stand-alone mode by strobing RT. WXI Write Expansion Input I Cascaded – Connected to WXO of previous device. Not Cascaded – Tied to VSS. RXI Read Expansion Input I Cascaded – Connected to RXO of previous device. Not Cascaded – Tied to VSS. RXO Read Expansion Output O Cascaded – Connected to RXI of next device. RS Reset I Resets device to empty condition. A reset is required before an initial read or write operation after power-up. OE Output Enable I When OE is LOW, the FIFO’s data outputs drive the bus to which they are connected. If OE is HIGH, the FIFO’s outputs are in High Z (high-impedance) state. VCC/SMODE Synchronous Almost Empty/ Almost Full Flags I Dual-Mode Pin: Asynchronous Almost Empty/Almost Full flags – tied to VCC. Synchronous Almost Empty/Almost Full flags – tied to VSS. (Almost Empty synchronized to RCLK, Almost Full synchronized to WCLK.) Document #: 38-06004 Rev. *C Data inputs for an 18-bit bus. Page 3 of 22 CY7C4255 CY7C4265 Maximum Ratings[1] Output Current into Outputs (LOW)............................. 20 mA (Above which the useful life may be impaired. For user guidelines, not tested.) Storage Temperature ................................–65°C to +150°C Ambient Temperature with Power Applied .–55°C to +125°C Static Discharge Voltage............................................ >2001V (per MIL–STD–883, Method 3015) Latch-Up Current ..................................................... >200 mA Operating Range[2] Supply Voltage to Ground Potential ............... –0.5V to +7.0V DC Voltage Applied to Outputs in High Z State ............................................... –0.5V to +7.0V Range Ambient Temperature VCC Commercial 0°C to +70°C DC Input Voltage ..........................................−0.5V to VCC+0.5V 5V ± 10% Industrial[3] –40°C to +85°C 5V ± 10% Electrical Characteristics Over the Operating Range[3] Parameter Description Test Conditions VOH Output HIGH Voltage VCC = Min., IOH = –2.0 mA VOL Output LOW Voltage VCC = Min., IOL = 8.0 mA VIH[4] Input HIGH Voltage [4] Input LOW Voltage VIL 7C42X5-10 7C42X5-15 7C42X5-25 7C42X5-35 Min. Min. Min. Min. Max. 2.4 0.4 2.0 Max. 2.4 0.4 VCC 2.0 Max. 2.4 0.4 VCC 2.0 Max. 2.4 VCC 2.0 Unit V 0.4 V VCC V –0.5 0.8 –0.5 0.8 –0.5 0.8 –0.5 0.8 V IIX Input Leakage Current VCC = Max. –10 +10 –10 +10 –10 +10 –10 +10 µA IOZL IOZH Output OFF, High Z Current OE > VIH, VSS < VO < VCC –10 +10 –10 +10 –10 +10 –10 +10 µA ICC1[5] Active Power Supply Current Com’l 45 mA Ind 50 50 50 50 mA ICC2[6] Average Standby Current Com’l 10 10 10 10 mA Ind 15 15 15 15 mA 45 45 45 Capacitance[7, 8] Parameter Description CIN Input Capacitance COUT Output Capacitance Test Conditions TA = 25°C, f = 1 MHz, VCC = 5.0V Max. Unit 5 pF 7 pF Notes: 1. The Voltage on any input or I/O pin cannot exceed the power pin during power-up. 2. TA is the “Instant On” case temperature. 3. See the last page of this specification for Group A subgroup testing information. 4. The VIH and VIL specifications apply for all inputs except WXI, RXI. The WXI, RXI pin is not a TTL input. It is connected to either RXO, WXO of the previous device or VSS. 5. Input signals switch from 0V to 3V with a rise/fall time of less than 3 ns, clocks and clock enables switch at 20 MHz, while data inputs switch at 10 MHz. Outputs are unloaded. ICC1(typical) = (25 mA + (freq – 20 MHz) * (1.0 mA/MHz)). 6. All inputs = VCC – 0.2V, except RCLK and WCLK (which are switching at frequency = 20 MHz), and FL/RT which is at VSS. All outputs are unloaded. 7. Tested initially and after any design changes that may affect these parameters. 8. Tested initially and after any process changes that may affect these parameters. Document #: 38-06004 Rev. *C Page 4 of 22 CY7C4255 CY7C4265 AC Test Loads and Waveforms[9, 10] R1 1.1 KΩ ALL INPUT PULSES 5V 3.0V OUTPUT CL GND ≤ 3 ns R2 680Ω INCLUDING JIG AND SCOPE Equivalent to: 90% 10% 90% 10% ≤ 3 ns THÉVENIN EQUIVALENT 410Ω OUTPUT 1.91V Switching Characteristics Over the Operating Range Parameter Description 7C42X5-10 7C42X5-15 7C42X5-25 7C42X5-35 Min. Min. Min. Min. Max. Max. Max. Max. Unit 28.6 MHz 20 ns tS Clock Cycle Frequency tA Data Access Time 2 tCLK Clock Cycle Time 10 tCLKH Clock HIGH Time 4.5 6 10 14 ns tCLKL Clock LOW Time 4.5 6 10 14 ns tDS Data Set-Up Time tDH Data Hold Time tENS Enable Set-Up Time tENH Enable Hold Time 100 8 66.7 2 10 15 40 2 15 25 2 35 ns 3 4 6 7 ns 0.5 1 1 2 ns 3 4 6 7 ns 0.5 1 1 2 ns tRS Reset Pulse Width[11] 10 15 25 35 ns tRSR Reset Recovery Time 8 10 15 20 ns tRSF Reset to Flag and Output Time tPRT Retransmit Pulse Width 30 35 45 55 ns tRTR Retransmit Recovery Time 60 65 75 85 ns tOLZ Output Enable to Output in Low Z[12] 0 0 0 0 ns tOE Output Enable to Output Valid 3 7 3 8 3 12 3 15 ns tOHZ Output Enable to Output in High Z[12] 3 7 3 8 3 12 3 15 ns tWFF Write Clock to Full Flag 8 10 15 20 ns tREF Read Clock to Empty Flag 8 10 15 20 ns 10 Flag[13] 15 25 35 ns tPAFasynch Clock to Programmable Almost-Full (Asynchronous mode, VCC/SMODE tied to VCC) 12 16 20 25 ns tPAFsynch Clock to Programmable Almost-Full Flag (Synchronous mode, VCC/SMODE tied to VSS) 8 10 15 20 ns tPAEasynch Clock to Programmable Almost-Empty Flag[13] (Asynchronous mode, VCC/SMODE tied to VCC) 12 16 20 25 ns tPAEsynch Clock to Programmable Almost-Full Flag (Synchronous mode, VCC/SMODE tied to VSS) 8 10 15 20 ns tHF Clock to Half-Full Flag 12 16 20 25 ns tXO Clock to Expansion Out 6 10 15 20 ns Notes: 9. CL = 30 pF for all AC parameters except for tOHZ. 10. CL = 5 pF for tOHZ. 11. Pulse widths less than minimum values are not allowed. 12. Values guaranteed by design, not currently tested. 13. tPAFasynch, tPAEasynch, after program register write will not be valid until 5 ns + tPAF(E). Document #: 38-06004 Rev. *C Page 5 of 22 CY7C4255 CY7C4265 Switching Characteristics Over the Operating Range (continued) Parameter Description 7C42X5-10 7C42X5-15 7C42X5-25 7C42X5-35 Min. Min. Min. Min. Max. Max. Max. Max. Unit tXI Expansion in Pulse Width 4.5 6.5 10 14 ns tXIS Expansion in Set-Up Time 4 5 10 15 ns tSKEW1 Skew Time between Read Clock and Write Clock for Full Flag 5 6 10 12 ns tSKEW2 Skew Time between Read Clock and Write Clock for Empty Flag 5 6 10 12 ns tSKEW3 Skew Time between Read Clock and Write Clock for Programmable Almost Empty and Programmable Almost Full Flags (Synchronous Mode only) 10 15 18 20 ns Document #: 38-06004 Rev. *C Page 6 of 22 CY7C4255 CY7C4265 Switching Waveforms Write Cycle Timing tCLK tCLKH tCLKL WCLK tDS tDH D0 –D17 tENS tENH WEN NO OPERATION tWFF tWFF FF tSKEW1 [14] RCLK REN Read Cycle Timing tCLK tCLKH tCLKL RCLK tENS tENH REN NO OPERATION tREF tREF EF tA Q0 –Q17 VALID DATA tOLZ tOHZ tOE OE tSKEW2[15] WCLK WEN Notes: 14. tSKEW1 is the minimum time between a rising RCLK edge and a rising WCLK edge to guarantee that FF will go HIGH during the current clock cycle. If the time between the rising edge of RCLK and the rising edge of WCLK is less than tSKEW1, then FF may not change state until the next WCLK rising edge. 15. tSKEW2 is the minimum time between a rising WCLK edge and a rising RCLK edge to guarantee that EF will go HIGH during the current clock cycle. It the time between the rising edge of WCLK and the rising edge of RCLK is less than tSKEW2, then EF may not change state until the next RCLK rising edge. Document #: 38-06004 Rev. *C Page 7 of 22 CY7C4255 CY7C4265 Switching Waveforms (continued) Reset Timing[16] tRS RS tRSR REN, WEN, LD tRSF EF,PAE tRSF FF,PAF, HF tRSF [17] OE = 1 Q0–Q17 OE = 0 First Data Word Latency after Reset with Simultaneous Read and Write WCLK tDS D0 –D17 D0 (FIRSTVALID WRITE) D1 tENS D2 D3 D4 [18] tFRL WEN tSKEW2 RCLK tREF EF REN tA Q0 –Q17 tA D0 tOLZ [19] D1 tOE OE Notes: 16. The clocks (RCLK, WCLK) can be free-running during reset. 17. After reset, the outputs will be LOW if OE = 0 and three-state if OE = 1. 18. When tSKEW2 > minimum specification, tFRL (maximum) = tCLK + tSKEW2. When tSKEW2 < minimum specification, tFRL (maximum) = either 2*tCLK + tSKEW2 or tCLK + tSKEW2. The Latency Timing applies only at the Empty Boundary (EF = LOW). 19. The first word is available the cycle after EF goes HIGH, always. Document #: 38-06004 Rev. *C Page 8 of 22 CY7C4255 CY7C4265 Switching Waveforms (continued) Empty Flag Timing WCLK tDS tDS D0 D0 –D17 D1 tENH tENS tENH tENS WEN tFRL[18] [18] tFRL RCLK tREF tSKEW2 tREF tREF tSKEW2 EF REN OE tA D0 Q0 –Q17 Full Flag Timing NO WRITE NO WRITE WCLK tSKEW1 [14] tDS tSKEW1 [14] DATA WRITE DATA WRITE D0 –D17 tWFF tWFF tWFF FF WEN RCLK tENS tENH tENS tENH REN OE LOW tA Q0 –Q17 DATA IN OUTPUT REGISTER Document #: 38-06004 Rev. *C tA DATA READ NEXT DATA READ Page 9 of 22 CY7C4255 CY7C4265 Switching Waveforms (continued) Half-Full Flag Timing tCLKH tCLKL WCLK tENS tENH WEN tHF HF HALF FULL + 1 OR MORE HALF FULL OR LESS HALF FULLOR LESS tHF RCLK tENS REN Programmable Almost Empty Flag Timing tCLKH tCLKL WCLK tENS tENH WEN tPAE PAE [20] N + 1 WORDS IN FIFO tPAE n WORDS IN FIFO RCLK tENS REN Note: 20. PAE is offset = n. Number of data words into FIFO already = n. Document #: 38-06004 Rev. *C Page 10 of 22 CY7C4255 CY7C4265 Switching Waveforms (continued) Programmable Almost Empty Flag Timing (applies only in SMODE (SMODE is LOW)) tCLKL tCLKH WCLK tENS tENH WEN WEN2 tENS tENH PAE tSKEW3 Note 21 [22] N + 1 WORDS INFIFO tPAE synch Note 23 tPAE synch RCLK tENS tENS tENH REN Programmable Almost Full Flag Timing tCLKL tCLKH Note 24 WCLK tENS tENH WEN tPAF PAF FULL– M WORDS [26] INFIFO [25] tPAF FULL– (M+1) WORDS [27] IN FIFO RCLK tENS REN Notes: 21. PAE offset − n. 22. tSKEW3 is the minimum time between a rising WCLK and a rising RCLK edge for PAE to change state during that clock cycle. If the time between the edge of WCLK and the rising RCLK is less than tSKEW3, then PAE may not change state until the next RCLK. 23. If a read is preformed on this rising edge of the read clock, there will be Empty + (n−1) words in the FIFO when PAE goes LOW. 24. PAF offset = m. Number of data words written into FIFO already = 8192 − (m + 1) for the CY7C4255 and 16384 − (m + 1) for the CY7C4265. 25. PAF is offset = m. 26. 8192 − m words in CY7C4255 and 16384 – m words in CY7C4265. 27. 8192 − (m + 1) words in CY7C4255 and 16384 – (m + 1) CY7C4265. Document #: 38-06004 Rev. *C Page 11 of 22 CY7C4255 CY7C4265 Switching Waveforms (continued) Programmable Almost Full Flag Timing (applies only in SMODE (SMODE is LOW)) Note 28 tCLKL tCLKH WCLK tENS tENH WEN Note 29 WEN2 tPAF tENS tENH PAF FULL– M [26] WORDS IN FIFO FULL– M + 1 WORDS IN FIFO tSKEW3[30] tPAF synch RCLK tENS tENS tENH REN Write Programmable Registers tCLK tCLKL tCLKH WCLK tENS tENH LD tENS WEN tDS tDH PAE OFFSET D0 –D17 PAE OFFSET PAF OFFSET D0 – D11 Notes: 28. If a write is performed on this rising edge of the write clock, there will be Full − (m − 1) words of the FIFO when PAF goes LOW. 29. PAF offset = m. 30. tSKEW3 is the minimum time between a rising RCLK and a rising WCLK edge for PAF to change state during that clock cycle. If the time between the edge of RCLK and the rising edge of WCLK is less than tSKEW3, then PAF may not change state until the next WCLK rising edge. Document #: 38-06004 Rev. *C Page 12 of 22 CY7C4255 CY7C4265 Switching Waveforms (continued) Read Programmable Registers tCLK tCLKL tCLKH RCLK tENS tENH LD tENS WEN tA UNKNOWN Q0 –Q17 PAE OFFSET PAF OFFSET PAE OFFSET Write Expansion Out Timing tCLKH WCLK Note 31 tXO Note 31 WXO tXO tENS WEN Read Expansion Out Timing tCLKH WCLK Note 32 tXO RXO tXO tENS REN Write Expansion In Timing tXI WXI WCLK tXIS Notes: 31. Write to Last Physical Location. 32. Read from Last Physical Location. Document #: 38-06004 Rev. *C Page 13 of 22 CY7C4255 CY7C4265 Switching Waveforms (continued) Read Expansion In Timing tXI RXI tXIS RCLK Retransmit Timing[33, 34, 35] FL/RT tPRT tRTR REN/WEN EF/FF and all async flags HF/PAE/PAF Notes: 33. Clocks are free-running in this case. 34. The flags may change state during Retransmit as a result of the offset of the read and write pointers, but flags will be valid at tRTR. 35. For the synchronous PAE and PAF flags (SMODE), an appropriate clock cycle is necessary after tRTR to update these flags. Document #: 38-06004 Rev. *C Page 14 of 22 CY7C4255 CY7C4265 Architecture The CY7C4256/65 consists of an array of 8K/16K words of 18 bits each (implemented by a dual-port array of SRAM cells), a read pointer, a write pointer, control signals (RCLK, WCLK, REN, WEN, RS), and flags (EF, PAE, HF, PAF, FF). The CY7C4255/65 also includes the control signals WXI, RXI, WXO, RXO for depth expansion. Resetting the FIFO normal read/write operation. When the LD pin is set LOW, and WEN is LOW, the next offset register in sequence is written. The contents of the offset registers can be read on the output lines when the LD pin is set LOW and REN is set LOW; then, data can be read on the LOW-to-HIGH transition of the Read Clock (RCLK). Table 1. Write Offset Register WCLK[36] LD WEN Upon power-up, the FIFO must be reset with a Reset (RS) cycle. This causes the FIFO to enter the Empty condition signified by EF being LOW. All data outputs go LOW after the falling edge of RS only if OE is asserted. In order for the FIFO to reset to its default state, a falling edge must occur on RS and the user must not read or write while RS is LOW. 0 0 Writing to offset registers: Empty Offset Full Offset 0 1 No Operation FIFO Operation 1 0 Write Into FIFO 1 1 No Operation When the WEN signal is active (LOW), data present on the D0–17 pins is written into the FIFO on each rising edge of the WCLK signal. Similarly, when the REN signal is active LOW, data in the FIFO memory will be presented on the Q0–17 outputs. New data will be presented on each rising edge of RCLK while REN is active LOW and OE is LOW. REN must set up tENS before RCLK for it to be a valid read function. WEN must occur tENS before WCLK for it to be a valid write function. Flag Operation An output enable (OE) pin is provided to three-state the Q0–17 outputs when OE is deasserted. When OE is enabled (LOW), data in the output register will be available to the Q0–17 outputs after tOE. If devices are cascaded, the OE function will only output data on the FIFO that is read enabled. Full Flag The FIFO contains overflow circuitry to disallow additional writes when the FIFO is full, and under flow circuitry to disallow additional reads when the FIFO is empty. An empty FIFO maintains the data of the last valid read on its Q0–17 outputs even after additional reads occur. Empty Flag Programming The CY7C4255/65 devices contain two 14-bit offset registers. Data present on D0–13 during a program write will determine the distance from Empty (Full) that the Almost Empty (Almost Full) flags become active. If the user elects not to program the FIFO’s flags, the default offset values are used (see Table 2). When the Load LD pin is set LOW and WEN is set LOW, data on the inputs D0–13 is written into the Empty offset register on the first LOW-to-HIGH transition of the Write Clock (WCLK). When the LD pin and WEN are held LOW then data is written into the Full offset register on the second LOW-to-HIGH transition of the Write Clock (WCLK). The third transition of the Write Clock (WCLK) again writes to the Empty offset register (see Table 1). Writing all offset registers does not have to occur at one time. One or two offset registers can be written and then, by bringing the LD pin HIGH, the FIFO is returned to Selection The CY7C4255/65 devices provide five flag pins to indicate the condition of the FIFO contents. Empty and Full are synchronous. PAE and PAF are synchronous if VCC/SMODE is tied to VSS. The Full Flag (FF) will go LOW when device is Full. Write operations are inhibited whenever FF is LOW regardless of the state of WEN. FF is synchronized to WCLK, i.e., it is exclusively updated by each rising edge of WCLK. The Empty Flag (EF) will go LOW when the device is empty. Read operations are inhibited whenever EF is LOW, regardless of the state of REN. EF is synchronized to RCLK, i.e., it is exclusively updated by each rising edge of RCLK. Programmable Almost Empty/Almost Full Flag The CY7C4255/65 features programmable Almost Empty and Almost Full Flags. Each flag can be programmed (described in the Programming section) a specific distance from the corresponding boundary flags (Empty or Full). When the FIFO contains the number of words or fewer for which the flags have been programmed, the PAF or PAE will be asserted, signifying that the FIFO is either Almost Full or Almost Empty. See Table 2 for a description of programmable flags. When the SMODE pin is tied LOW, the PAF flag signal transition is caused by the rising edge of the write clock and the PAE flag transition is caused by the rising edge of the read clock. Note: 36. The same selection sequence applies to reading from the registers. REN is enabled and read is performed on the LOW-to-HIGH transition of RCLK. Document #: 38-06004 Rev. *C Page 15 of 22 CY7C4255 CY7C4265 Retransmit The retransmit feature is beneficial when transferring packets of data. It enables the receipt of data to be acknowledged by the receiver and retransmitted if necessary. The Retransmit (RT) input is active in the stand-alone and width expansion modes. The retransmit feature is intended for use when a number of writes equal to or less than the depth of the FIFO have occurred and at least one word has been read since the last RS cycle. A HIGH pulse on RT resets the internal read pointer to the first physical location of the FIFO. WCLK and RCLK may be free running but must be disabled during and tRTR after the retransmit pulse. With every valid read cycle after retransmit, previously accessed data is read and the read pointer is incremented until it is equal to the write pointer. Flags are governed by the relative locations of the read and write pointers and are updated during a retransmit cycle. Data written to the FIFO after activation of RT are transmitted also. The full depth of the FIFO can be repeatedly retransmitted. Table 2. Flag Truth Table Number of Words in FIFO CY7C4255 – 8K x 18 CY7C4265 – 16K x 18 FF PAF HF PAE EF 0 0 H H H L L 1 to n[37] 1 to n[37] H H H L H (n + 1) to 4096 (n + 1) to 8192 H H H H H 4097 to (8192 – (m + 1)) 8193 to (16384 – (m + 1)) H H L H H (8192 – m)[38] to 8191 (16384 – m)[38] to 16383 H L L H H 8192 16384 L L L H H Notes: 37. n = Empty Offset (Default Values: CY7C4255/CY7C4265 n = 127). 38. m = Full Offset (Default Values: CY7C4255/CY7C4265 n = 127). Document #: 38-06004 Rev. *C Page 16 of 22 CY7C4255 CY7C4265 Width Expansion Configuration ANDing the Empty (Full) flags of every FIFO; the PAE and PAF flags can be detected from any one device. This technique will avoid reading data from, or writing data to the FIFO that is “staggered” by one clock cycle due to the variations in skew between RCLK and WCLK. Figure 1 demonstrates a 36-word width by using two CY7C4255/65s. The CY7C4255/65 can be expanded in width to provide word widths greater than 18 in increments of 18. During width expansion mode all control line inputs are common and all flags are available. Empty (Full) flags should be created by RESET (RS) DATA IN (D) 36 RESET (RS) 18 18 READ CLOCK (RCLK) WRITE CLOCK (WCLK) READ ENABLE (REN) WRITE ENABLE (WEN) OUTPUT ENABLE (OE) LOAD (LD) PROGRAMMABLE(PAE) 7C4255 7C4265 7C4255 7C4265 HALF FULL FLAG (HF) PROGRAMMABLE (PAF) EMPTY FLAG (EF) FF FF EF EF 18 FULL FLAG (FF) DATA OUT (Q) 36 18 FIRST LOAD (FL) WRITE EXPANSION IN (WXI) READ EXPANSION IN (RXI) Figure 1. Block Diagram of 8K x18/16K x 18 Synchronous FIFO Memory Used in a Width Expansion Configuration Document #: 38-06004 Rev. *C Page 17 of 22 CY7C4255 CY7C4265 Depth Expansion Configuration (with Programmable Flags) 3. The Write Expansion Out (WXO) pin of each device must be tied to the Write Expansion In (WXI) pin of the next device. The CY7C4255/65 can easily be adapted to applications requiring more than 8192/16384 words of buffering. Figure 2 shows Depth Expansion using three CY7C42X5s. Maximum depth is limited only by signal loading. Follow these steps: 4. The Read Expansion Out (RXO) pin of each device must be tied to the Read Expansion In (RXI) pin of the next device. 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. 5. All Load (LD) pins are tied together. 6. The Half-Full Flag (HF) is not available in the Depth Expansion Configuration. 7. EF, FF, PAE, and PAF are created with composite flags by ORing together these respective flags for monitoring. The composite PAE and PAF flags are not precise. WXO RXO 7C4255 7C4265 VCC FL FF EF PAE PAF WXI RXI WXO RXO 7C4255 7C4265 DATA IN(D) DATA OUT (Q) VCC FL FF EF PAF PAE WXI RXI WRITE CLOCK(WCLK) WXO RXO WRITE ENABLE(WEN) READ ENABLE(REN) 7C4255 7C4265 RESET (RS) READ CLOCK(RCLK) OUTPUT ENABLE(OE) LOAD (LD) FF FF PAF EF EF PAFWXI RXI PAE PAE FIRST LOAD (FL) Figure 2. Block Diagram of 8Kx18/16Kx18 Synchronous FIFO Memory with Programmable Flags used in Depth Expansion Configuration Document #: 38-06004 Rev. *C Page 18 of 22 CY7C4255 CY7C4265 Typical AC and DC Characteristics NORMALIZED tA vs. AMBIENT TEMPERATURE NORMALIZED tA vs. SUPPLY VOLTAGE 1.60 NORMALIZED tA NORMALIZED tA 1.20 1.10 1.00 0.90 TA = 25°C 0.80 4.00 4.50 5.00 5.50 6.00 1.40 1.20 1.00 0.60 −55.00 VIN = 3.0V TA = 25°C f = 28 MHz 0.80 4.50 5.00 5.50 SUPPLY VOLTAGE (V) Document #: 38-06004 Rev. *C 6.00 NORMALIZED ICC NORMALIZED ICC NORMALIZED ICC 1.00 125.00 1.75 1.20 1.20 65.00 NORMALIZED SUPPLY CURRENT vs. FREQUENCY NORMALIZED SUPPLY CURRENT vs. AMBIENT TEMPERATURE 1.40 0.60 4.00 5.00 AMBIENT TEMPERATURE (°C) SUPPLY VOLTAGE (V) NORMALIZED SUPPLY CURRENT vs. SUPPLY VOLTAGE VCC = 5.0V 0.80 1.10 1.00 VIN = 3.0V VCC = 5.0V f = 28 MHz 0.90 0.80 −55.00 5.00 65.00 125.00 AMBIENT TEMPERATURE (°C) 1.50 1.25 1.00 VCC = 5.0V TA = 25°C VIN = 3.0V 0.75 0.50 20.00 30.00 40.00 50.00 60.00 FREQUENCY (MHz) Page 19 of 22 CY7C4255 CY7C4265 Ordering Information 8Kx18 Deep Sync FIFO Speed (ns) 10 15 Ordering Code Package Name Package Type CY7C4255–10AC A65 64-Lead Thin Quad Flatpack CY7C4255–10AXC A65 64-Lead Pb-Free Thin Quad Flatpack CY7C4255–10ASC A64 64-Lead Small Thin Quad Flatpack CY7C4255–15AC A65 64-Lead Thin Quad Flatpack CY7C4255–15AXC A65 64-Lead Pb-Free Thin Quad Flatpack Operating Range Commercial Commercial 16Kx18 Deep Sync FIFO Speed (ns) 10 15 Ordering Code Package Name Package Type CY7C4265–10AC A65 64-Lead Thin Quad Flatpack CY7C4265–10ASC A64 64-Lead Small Thin Quad Flatpack CY7C4265–10ASXC A64 64-Lead Pb-Free Small Thin Quad Flatpack CY7C4265–10AI A65 64-Lead Thin Quad Flatpack CY7C4265–10AXI A65 64-Lead Pb-Free Thin Quad Flatpack CY7C4265–15AC A65 64-Lead Thin Quad Flatpack CY7C4265–15AXC A65 64-Lead Pb-Free Thin Quad Flatpack CY7C4265-15ASC A64 64-Lead Small Thin Quad Flatpack Operating Range Commercial Industrial Commercial Package Diagrams 64-Pin Thin Plastic Quad Flat Pack (10 x 10 x 1.4 mm) A64 64-Pin Pb-Free Thin Plastic Quad Flat Pack (10 x 10 x 1.4 mm) A64 51-85051-A Document #: 38-06004 Rev. *C Page 20 of 22 CY7C4255 CY7C4265 Package Diagrams (continued) 64-Lead Thin Plastic Quad Flat Pack (14 x 14 x 1.4 mm) A65 64-Lead Pb-Free Thin Plastic Quad Flat Pack (14 x 14 x 1.4 mm) A65 51-85046-*B All products and company names mentioned in this document may be the trademarks of their respective holders. Document #: 38-06004 Rev. *C Page 21 of 22 © Cypress Semiconductor Corporation, 2005. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges. CY7C4255 CY7C4265 Document History Page Document Title: CY7C4255, CY7C4265 8K/16K X 18 Deep Sync FIFOs Document Number: 38-06004 REV. ECN NO. Issue Date Orig. of Change Description of Change ** 106465 07/11/01 SZV Change from Spec Number: 38-00468 to 38-06004 *A 122257 12/26/02 RBI Power up requirements added to Maximum Ratings Information *B 252889 See ECN YDT Removed PLCC package and pruned parts from Order Information *C 385985 See ECN ESH Added Pb-Free logo to top of first page Added CY7C4265-10ASXC, CY7C4265-10AXI, CY7C4265-15AXC, CY7C4255-10AXC, CY7C4255-15AXC to ordering information Document #: 38-06004 Rev. *C Page 22 of 22