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CY7C451 CY7C453 CY7C454
512x9, 2Kx9, and 4Kx9 Cascadable Clocked FIFOs with Programmable
Features
* High-speed, low-power, first-in first-out (FIFO) memories * 512 x 9 (CY7C451) * 2,048 x 9 (CY7C453) * 4,096 x 9 (CY7C454) * 0.65 micron CMOS for optimum speed/power * High-speed 83-MHz operation (12 ns read/write cycle time) * Low power -- ICC=70 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 * Parity generation/checking * 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 * Width Expansion Capability * Depth Expansion Capability * Available in PLCC packages and write interfaces. Both FIFOs are 9 bits wide. The CY7C451 has a 512-word by 9-bit memory array, the CY7C453 has a 2048-word by 9-bit memory array, and the CY7C454 has a 4096-word by 9-bit memory array. Devices can be cascaded to increase FIFO depth. Programmable features include Almost Full/Empty flags and generation/checking of parity. These FIFOs provide solutions for a wide variety of data buffering needs, including high-speed data acquisition, multiprocessor interfaces, and communications buffering. Both FIFOs have 9-bit input and output ports that are controlled by separate clock and enable signals. The input port is controlled by a free-running clock (CKW) and a write enable pin (ENW). When ENW is asserted, data is written into the FIFO on the rising edge of the CKW signal. While ENW is held active, data is continually written into the FIFO on each CKW cycle. The output port is controlled in a similar manner by a free-running read clock (CKR) and a read enable pin (ENR). The read (CKR) and write (CKW) 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 83.3 MHz are achievable in the standalone configuration, and up to 83.3 MHz is achievable when FIFOs are cascaded for depth expansion. Depth expansion is possible using the cascade input (XI) and cascade output (XO). The XO signal is connected to the XI of the next device, and the XO of the last device should be connected to the XI of the first device. In standalone mode, the input (XI) pin is simply tied to VSS. In the standalone and width expansion configurations, a LOW on the retransmit (RT) input causes the FIFOs to retransmit the data. Read enable (ENR) and the write enable (ENW) must both be HIGH during the retransmit, and then ENR is used to access the data.
Functional Description
The CY7C451, CY7C453, and CY7C454 are high-speed, low-power, first-in first-out (FIFO) memories with clocked read
Logic Block Diagram
D0 - 8
Pin Configurations
INPUT REGISTER
CKW
ENW FLAG/PARITY PROGRAM REGISTER
PLCC/LCC Top View
D0 D1 D2 D3 D4 D5 D6 PARITY
WRITE CONTROL
FLAG LOGIC RAM ARRAY 512x 9 2048x 9 4096x9
HF E/F PAFE/XO
WRITE POINTER MR FL/RT
READ POINTER
XI ENW CKW VCC VSS HF E/F PAFE/XO Q0
5 6 7 7C451 8 7C453 9 7C454 10 11 12 13 14 15 16 17 1819
4 3 2 1 32 31 30 29 28 27 26 25 24 23 22 21 20
D7 D8 FL/RT MR VSS CKR ENR OE Q8 /PG/PE
Q1 Q2 Q3 Q4 Q5 Q6 Q7 RESET LOGIC TRI-STATE OUTPUT REGISTER OE RETRANSMIT LOGIC Q0-7,Q8/PG/PE CKR ENR C451-1
C451-2
XI
EXPANSION LOGIC
READ CONTROL
Cypress Semiconductor Corporation Document #: 38-06033 Rev. *A
*
3901 North First Street
*
San Jose
*
CA 95134 * 408-943-2600 Revised December 27, 2002
CY7C451 CY7C453 CY7C454
Functional Description (continued)
The CY7C451, CY7C453, and CY7C454 provide three status pins to the user. These pins are decoded to determine one of six states: Empty, Almost Empty, Less than or Equal to Half Full, Greater than Half Full, Almost Full, and Full (see Table 1). The Almost Empty/Full flag (PAFE) and XO functions share the same pin. The Almost Empty/Full flag is valid in the standalone and width expansion configurations. In the depth expansion, this pin provides the expansion out (XO) information that is used to signal the next FIFO when it will be activated. The flags are synchronous, i.e., they change state relative to either the read clock (CKR) or the write clock (CKW). When entering or exiting the Empty and Almost Empty states, the flags are updated exclusively by the CKR. The flags denoting Half Full, Almost Full, and Full states are updated exclusively by CKW. The synchronous flag architecture guarantees that the flags maintain their status for some minimum time. The CY7C451, CY7C453, and the CY7C454 use center power and ground for reduced noise. Both configurations are fabricated using an advanced RAM 2.8 technology. Input ESD protection is greater than 2001V, and latch-up is prevented by the use of reliable layout techniques and guard rings.
Selection Guide
7C451-12 7C453-12 7C454-12 Maximum Frequency (MHz) Maximum Cascadable Frequency Maximum Access Time (ns) Minimum Cycle Time (ns) Minimum Clock HIGH Time (ns) Minimum Clock LOW Time (ns) Minimum Data or Enable Set-Up (ns) Minimum Data or Enable Hold (ns) Maximum Flag Delay (ns) Maximum Current (mA) Commercial Military/Industrial Selection Guide (continued) CY7C451 Density OE, Depth Cascadable Package 512 x 9 Yes 32-Pin PLCC CY7C453 2,048 x 9 Yes 32-Pin PLCC CY7C454 4,096 x 9 Yes 32-Pin PLCC 83.3 83.3 9 12 5 5 4 0 9 140 150 7C451-14 7C453-14 7C454-14 71.4 71.4 10 14 6.5 6.5 5 0 10 140 150 7C451-20 7C453-20 7C454-20 50 50 15 20 9 9 6 0 15 120 130 7C451-30 7C453-30 7C454-30 33.3 33.3 20 30 12 12 7 0 20 100 110
Maximum Ratings[1]
(Above which the useful life may be impaired. For user guidelines, not tested.) Storage Temperature ....................................-65C to +150C Ambient Temperature with Power Applied.................................................-55C to +125C Supply Voltage to Ground Potential .................-0.5V to +7.0V DC Voltage Applied to Outputs in High Z State .....................................................-0.5V to +7.0V DC Input Voltage .................................................-3.0V to +7.0V
Notes: 1. The Voltage on any input or I/O pin cannot exceed the power pin during power-up.
Output Current into Outputs (LOW)............................. 20 mA Static Discharge Voltage............................................ >2001V (per MIL-STD-883, Method 3015) Latch-Up Current.................................................... > 200 mA
Operating Range
Range Commercial Industrial Ambient Temperature 0C to +70C -40C to +85C VCC 5V 10% 5V 10%
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Pin Definitions
Signal Name D0 - 8 I/O I Description Data Inputs: When the FIFO is not full and ENW is active, CKW (rising edge) writes data (D0 - 8) into the FIFO's memory. If MR is asserted at the rising edge of CKW then data is written into the FIFO's programming register. D8 is ignored if the device is configured for parity generation. Data Outputs: When the FIFO is not empty and ENR is active, CKR (rising edge) reads data (Q0 - 7) out of the FIFO's memory. If MR is active at the rising edge of CKR then data is read from the programming register. Function varies according to mode: Parity disabled - same function as Q0 - 7 Parity enabled, generation - parity generation bit (PG) Parity enabled, check - Parity Error Flag (PE) Enable Write: enables the CKW input (for both non-program and program modes) Enable Read: enables the CKR input (for both non-program and program modes) Write Clock: the rising edge clocks data into the FIFO when ENW is LOW; updates Half Full, Almost Full, and Full flag states. When MR is asserted, CKW writes data into the program register. Read Clock: the rising edge clocks data out of the FIFO when ENR is LOW; updates the Empty and Almost Empty flag states. When MR is asserted, CKR reads data out of the program register. Half Full Flag - synchronized to CKW. Empty or Full Flag - E is synchronized to CKR; F is synchronized to CKW Dual-Mode Pin: Not Cascaded - Programmable Almost Full is synchronized to CKW; Programmable Almost Empty is synchronized to CKR Cascaded - Expansion Out signal, connected to XI of next device Not Cascaded - XI is tied to VSS Cascaded - Expansion Input, connected to XO of previous device First Load/ Retransmit Pin: Cascaded - the first device in the daisy chain will have FL tied to VSS; all other devices will have FL tied to VCC (Figure 2) Not Cascaded - tied to VCC; Retransmit function is also available in stand alone mode by strobing RT Master Reset: resets device to empty condition. Non-Programming Mode: program register is reset to default condition of no parity and PAFE active at 16 or less locations from Full/Empty. Programming Mode: Data present on D0 - 8 is written into the programmable register on the rising edge of CKW. Program register contents appear on Q 0 - 8 after the rising edge of CKR. Output Enable for Q0 - 7 and Q8/PG/PE pins
Q0 - 7
O
Q8/PG/PE
O
ENW ENR CKW CKR HF E/F PAFE/XO
I I I I O O O
XI FL/RT
I I
MR
I
OE
I
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CY7C451 CY7C453 CY7C454
Electrical Characteristics Over the Operating Range
7C451-12 7C453-12 7C454-12 Parameter VOH VOL VIH[2] VIL[2] IIX IOS[3] IOZL IOZH ICC1[4] ICC2
[5]
7C451-14 7C453-14 7C454-14 2.4
7C451-20 7C453-20 7C454-20 2.4
7C451-30 7C453-30 7C454-30 2.4 V 0.4 2.2 -0.5 -10 -90 VCC 0.8 +10 V V V A mA +10 100 110 70 80 30 30 A mA mA mA mA mA mA
Description Output HIGH Voltage Output LOW Voltage Input HIGH Voltage Input LOW Voltage Input Leakage Current Output Short Circuit Current Output OFF, High Z Current Operating Current Operating Current Standby Current
Test Conditions VCC = Min., IOH = -2.0 mA VCC = Min., IOL = 8.0 mA
Min. Max. Min. Max. Min. Max. Min. Max. Unit 2.4 0.4 2.2 -0.5 VCC 0.8 +10 2.2 -0.5 -10 -90 +10 140 150 70 80 30 30 -10 +10 140 150 70 80 30 30
0.4 VCC 0.8 +10 2.2 -0.5 -10 -90 -10
0.4 VCC 0.8 +10
VCC = Max. VCC = Max., VOUT = GND OE > VIH, VSS < VO < VCC VCC = Max., IOUT = 0 mA VCC = Max., IOUT = 0 mA VCC = Max., IOUT = 0 mA Com'l Mil/Ind Com'l Mil/Ind Com'l Mil/Ind
-10 -90 -10
+10 120 130 70 80 30 30
-10
ISB[6]
Capacitance[7]
Parameter CIN COUT Description Input Capacitance Output Capacitance Test Conditions TA = 25C, f = 1 MHz, VCC = 5.0V Max. 10 12 Unit pF pF
Notes: 2. The VIH and VIL specifications apply for all inputs except XI. The XI pin is not a TTL input. It is connected to either XO of the previous device or VSS . 3. Test no more than one output at a time for not more than one second. 4. Input signals switch from 0V to 3V with a rise/fall time of less than 3 ns, clocks and clock enables switch at maximum frequency (fMAX), while data inputs switch at f MAX/2. Outputs are unloaded. 5. Input signals switch from 0V to 3V with a rise/fall time less than 3 ns, clocks and clock enables switch at 20 MHz, while the data inputs switch at 10 MHz. Outputs are unloaded. 6. All input signals are connected to VCC. All outputs are unloaded. Read and write clocks switch at maximum frequency (fMAX ). 7. Tested initially and after any design or process changes that may affect these parameters.
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AC Test Loads and Waveforms[8, 9, 10, 11, 12]
R1500 5V OUTPUT CL INCLUDING JIG AND SCOPE Equivalent to: THEVENIN EQUIVALENT 200 OUTPUT 2V R2 333 3.0V GND < 3 ns
ALL INPUT PULSES
90% 10% 90% 10% < 3 ns
C451-5
C451-4
Switching Characteristics Over the Operating Range[13]
7C451-12 7C453-12 7C454-12 Parameter tCKW tCKR tCKH tCKL tA[14] tOH tFH tSD tHD tSEN tHEN tOE tOLZ[7,15] tOHZ tPG tPE tFD tSKEW1
[16] [7,15]
7C451-14 7C453-14 7C454-14 Min. 14 14 6.5 6.5 Max.
7C451-20 7C453-20 7C454-20 Min. 20 20 9 9 Max.
7C451-30 7C453-30 7C454-30 Min. 30 30 12 12 Max. Unit ns ns ns ns 20 0 0 7 0 7 0 ns ns ns ns ns ns ns 20 0 20 20 20 20 0 ns ns ns ns ns ns ns
Description Write Clock Cycle Read Clock Cycle Clock HIGH Clock LOW Data Access Time Previous Output Data Hold After Read HIGH Previous Flag Hold After Read/Write HIGH Data Set-Up Data Hold Enable Set-Up Enable Hold OE LOW to Output Data Valid OE LOW to Output Data in Low Z OE HIGH to Output Data in High Z Read HIGH to Parity Generation Read HIGH to Parity Error Flag Flag Delay Opposite Clock After Clock
Min. 12 12 5 5
Max.
9 0 0 4 0 4 0 9 0 9 9 9 9 0 0 0 0 0 5 0 5 0
10 0 0 6 0 6 0 10 0 10 10 10 10 0
15
15 15 15 15 15
Notes: 8. CL = 30 pF for all AC parameters except for tOHZ . 9. CL = 5 pF for tOHZ . 10. All AC measurements are referenced to 1.5V except tOE , tOLZ, and tOHZ. 11. tOE and t OLZ are measured at 100 mV from the steady state. 12. tOHZ is measured at +500 mV from VOL and - 500 mV from VOH . 13. Test conditions assume signal transition time of 3 ns or less, timing reference levels of 1.5V, and output loading as shown in AC Test Loads and Waveforms and capacitance as in notes 8 and 9, unless otherwise specified. 14. Access time includes all data outputs switching simultaneously. 15. At any given temperature and voltage condition, tOLZ is greater than t OHZ for any given device. 16. tSKEW1 is the minimum time an opposite clock can occur after a clock and still be guaranteed not to be included in the current clock cycle (for purposes of flag update). If the opposite clock occurs less than t SKEW1 after the clock, the decision of whether or not to include the opposite clock in the current clock cycle is arbitrary. Note: The opposite clock is the signal to which a flag is not synchronized; i.e., CKW is the opposite clock for Empty and Almost Empty flags, CKR is the opposite clock for the Almost Full, Half Full, and Full flags. The clock is the signal to which a flag is synchronized; i.e., CKW is the clock for the Half Full, Almost Full, and Full flags, CKR is the clock for Empty and Almost Empty flags.
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CY7C451 CY7C453 CY7C454
Switching Characteristics Over the Operating Range[13] (continued)
7C451-12 7C453-12 7C454-12 Parameter tSKEW2[17] tPMR tSCMR tOHMR tMRR Description Opposite Clock Before Clock Master Reset Pulse Width (MR LOW) Last Valid Clock LOW Set-Up to MR LOW Data Hold From MR LOW Master Reset Recovery (MR HIGH Set-Up to First Enabled Write/Read) MR HIGH to Flags Valid MR HIGH to Data Outputs LOW Program Mode--MR LOW Set-Up Program Mode--MR LOW Hold Program Mode--Write HIGH to Read HIGH Program Mode--Data Access Time Program Mode--Data Hold Time from MR HIGH Retransmit Pulse Width Retransmit Recovery Time 0 12 12 12 9 12 12 0 14 14 Min. 12 12 0 0 12 Max. 7C451-14 7C453-14 7C454-14 Min. 14 14 0 0 14 Max. 7C451-20 7C453-20 7C454-20 Min. 20 20 0 0 20 Max. 7C451-30 7C453-30 7C454-30 Min. 30 30 0 0 30 Max. Unit ns ns ns ns ns
tMRF tAMR tSMRP tHMRP tFTP tAP tOHP tPRT tRTR
12 12 14 10 14
14 14 20 15 20 14 0 20 20
20 20 30 25 30 20 0 30 30
30 30
ns ns ns ns ns
30
ns ns
17. tSKEW2 is the minimum time an opposite clock can occur before a clock and still be guaranteed to be included in the current clock cycle (for purposes of flag update). If the opposite clock occurs less than t SKEW2 before the clock, the decision of whether or not to include the opposite clock in the current clock cycle is arbitrary. See Note 16 for definition of clock and opposite clock.
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CY7C451 CY7C453 CY7C454
Switching Waveforms
Write Clock Timing Diagram
tCKH CKW tSD D0 - 8
VALID DATA IN ENABLED WRITE
tCKW tCKL
DISABLED WRITE
tHD
tSEN ENW tFH E/F, PAFE,HF
tHEN
tSEN
tHEN
tFD
tFH
tFD
C451-6
Read Clock Timing Diagram
tCKH CKR
tCKR
tCKL
DISABLED READ
ENABLED READ
tOH Q0 - 8
PREVIOUS WORD
tA
NEW WORD
tSEN ENR tFH E/F,PAFE
tHEN
tSEN
tHEN
tFD
tFH
tFD
C451-7
Master Reset (Default with Free-Running Clocks) Timing Diagram
tPMR MR tSCMR CKW ENW tSCMR CKR ENR tOHMR Q0 - 8
VALID DATA
[18,19,20,21]
tMRR
FIRST WRITE
tMRR
tAMR
ALL DATA OUTPUTS LOW
tMRF E/F,PAFE tMRF HF
Notes: 18. To only perform reset (no programming), the following criteria must be met: ENW or CKW must be inactive while MR is LOW. 19. To only perform reset (no programming), the following criteria must be met: ENR or CKR must be inactive while MR is LOW. 20. All data outputs (Q0 - 8 ) go LOW as a result of the rising edge of MR after t AMR. 21. In this example, Q0 - 8 will remain valid until t OHMR if either the first read shown did not occur or if the read occurred soon enough such that the valid data was caused by it.
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CY7C451 CY7C453 CY7C454
Switching Waveforms (continued)
Master Reset (Programming Mode) Timing Diagram
tSMRP MR tSCMR CKW ENW
LOW LAST VALID WRITE
[20,21]
tHMRP
tCKH
PGM WRITE
tMRR
FIRST WRITE SECOND WRITE
tFTP tSD tHD
PGM WORD WORD 1 WORD 2
D0- 8
LAST WORD
tSCMR CKR ENR
LAST VALID READ LOW
tSMRP
PGM READ
tHMRP
tCKH tOHMR tAP tOHP
PGM WORD
tAMR
ALL DATA OUTPUTS L OW C451-9
Q0- 8
VALID DATA
Master Reset (Programming Mode with Free-Running Clocks) Timing Diagram
tSMRP MR tSCMR CKW
LAST VALID WRITE
[20,21]
tHMRP tCKW tCKH
PGM WRITE
tCKL
tMRR
FIRST WRITE SECOND WRITE
tSEN ENW
tHEN
tFTP D0- 8
LAST WORD PGM WORD WORD 1 WORD 2
tCKR tSCMR CKR
LAST VALID READ
tSMRP
PGM READ
tHMRP
tMRR
tCKH tSEN tHEN
tCKL
ENR tAMR
ALL DATA OUTPUTS L OW C451-10
tOHMR Q0- 8
VALID DATA
tAP
tOHP
PGM WORD
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CY7C451 CY7C453 CY7C454
Switching Waveforms (continued)
Read to Empty Timing Diagram
COUNT 3 2
[22,25,26]
1 0 1 1 (NO CHANGE) LATENTCYCLE 0
CKR
R1 ENABLED READ
R2 ENABLED READ
R3 ENABLED READ
R4 FLAG UPDATE READ
R5 ENABLED READ
ENR tSKEW1 CKW
LOW
tSKEW2
W1 ENABLED WRITE
ENW tFD E/F PAFE
LOW C451-12
tFD
tFD
Read to Empty Timing Diagram with Free-Running Clocks
COUNT 1 0 R1 ENABLED READ R2 IGNORED READ 1 R3 IGNORED READ
[22,23,24,25]
LATENTCYCLE 0 R5 ENABLED READ R6 IGNORED READ
CKR
tSKEW2 ENR tSKEW1 CKW
W1 W2 W3 ENABLED WRITE
R4 FLAG UPDATE READ
tSKEW2
W4 W5 W6
ENW
HIGH
HF tFD E/F PAFE
LOW C451-11
tFD
tFD
Notes: 22. "Count" is the number of words in the FIFO. 23. The FIFO is assumed to be programmed with P>0 (i.e., PAFE does not transition at Empty or Full). 24. R2 is ignored because the FIFO is empty (count = 0). It is important to note that R3 is also ignored because W3, the first enabled write after empty, occurs less than tSKEW2 before R3. Therefore, the FIFO still appears empty when R3 occurs. Because W3 occurs greater than t SKEW2 before R4, R4 includes W3 in the flag update. 25. CKR is clock; CKW is opposite clock. 26. R3 updates the flag to the Empty state by asserting E/F. Because W1 occurs greater than t SKEW1 after R3, R3 does not recognize W1 when updating flag status. But because W1 occurs greater than tSKEW2 before R4, R4 includes W1 in the flag update and, therefore, updates FIFO to Almost Empty state. It is important to note that R4 is a latent cycle; i.e., it only updates the flag status regardless of the state of ENR. It does not change the count or the FIFO's data outputs.
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CY7C451 CY7C453 CY7C454
Switching Waveforms (continued)
Read to Almost Empty Timing Diagram with Free-Running Clocks
COUNT 17 16 R1 ENABLED READ 17 R2 18 R3
[22,25,27]
17 R4 ENABLED READ 16 R5 ENABLED READ 15 R6 ENABLED READ
CKR
ENR tSKEW1 CKW
W1
W2 ENABLED WRITE
tSKEW2
W3 ENABLED WRITE
W4
W5 W1
W6
ENW
HIGH
HF
HIGH
E/F
tFD PAFE
tFD
tFD
C451-14
Read to Almost Empty Timing Diagram with Read Flag Cycle and Update Free-Running Clocks
18 (no change) COUNT 17 16 17 18 FLAG UPDATE CYCLE 17 16
[22,25,27,28,29]
15
CKR
R1 ENABLED READ
R2
R3
R4 FLAG UPDATE READ
R5 ENABLED READ
R6 ENABLED READ
R7 ENABLED READ
ENR tSKEW1 CKW
W1
W2 ENABLED WRITE
tSKEW2
W3 ENABLED WRITE
W4
W5
W6
W7
ENW HF
HIGH
E/F
HIGH
tFD PAFE
tFD
tFD
C451-13
Notes: 27. The FIFO in this example is assumed to be programmed to its default flag values. Almost Empty is 16 words from Empty; Almost Full is 16 locations from Full. 28. R4 only updates the flag status. It does not affect the count because ENR is HIGH. 29. When making the transition from Almost Empty to Intermediate, the count must increase by two (16 =>18; two enabled writes: W2, W3) before a read (R4) can update flags to the Less Than Half Full state.
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CY7C451 CY7C453 CY7C454
Switching Waveforms (continued)
Write to Half Full Timing Diagram with Free-Running Clocks
COUNT 1024 [256] 1025 [257] W1 ENABLED WRITE 1024 [256] W2 1023 [255] W3
[22,30,31,32]
1024 [256] W4 ENABLED WRITE
1025 [257] W5 ENABLED WRITE
1026 [258] W6 ENABLED WRITE
CKW
ENW tSKEW1 CKR
R1
R2 ENABLED READ
tSKEW2
R3 ENABLED READ
R4
R5
R6
ENR tFD HF
HIGH
tFD
tFD
E/F
HIGH
PAFE
C451-15
Write to Half Full Timing Diagram with Write Flag Update Cycle with Free-Running Clocks
1023 (no change) [255] COUNT 1024 [256] 1025 [257] W1 ENABLED WRITE 1024 [256] W2 1023 [255] W3 FLAG UPDATE CYCLE 1024 [256] W5 ENABLED WRITE 1025 [257]
[22,30,31,32,33,34]
1026 [258] W7 ENABLED WRITE
CKW
W4 FLAG UPDATE WRITE
W6 ENABLED WRITE
ENW tSKEW1 CKR
R1
R2 ENABLED READ
tSKEW2
R3 ENABLED READ
R4
R5
R6
R7
ENR tFD HF E/F PAFE
HIGH
tFD
tFD
HIGH C451-16
Notes: 30. CKW is clock and CKR is opposite clock. 31. Count = 2,049 indicates Half Full for the CY7C454, count=1,025 indicates Half Full for the CY7C453, and count = 257 indicates Half Full for the CY7C451. Values for CY7C451 count are shown in brackets. 32. When the FIFO contains 2048[1024,256] words, the rising edge of the next enabled write causes the HF to be true (LOW). 33. The HF write flag update cycle does not affect the count because ENW is HIGH. It only updates HF to HIGH. 34. When making the transition from Half Full to Less Than Half Full, the count must decrease by two (1,025 =>1,023; two enabled reads: R2 and R3) before a write (W4) can update flags to less than Half Full.
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CY7C451 CY7C453 CY7C454
Switching Waveforms (continued)
Write to Almost Full Timing Diagram
COUNT 2030 [494] 2031 [495] 2032 [496]
[22,27,30,35,36]
2031 [495] 2030 [494] 2031 [495] 2030 [494] 2032 [496] 2031 [495] W4 ENABLED WRITE 2033 [497] 2032 [496] W5 ENABLED WRITE
CKW
W1 ENABLED WRITE
W2 ENABLED WRITE
W3 ENABLED WRITE FLAG UPDATE
ENW tSKEW1 CKR ENR tFD PAFE HF E/F
LOW R1 ENABLED READ R2 ENABLED READ
tSKEW2
tFD
tFD
tFD
HIGH C451-18
Write to Almost Full Timing Diagram with Free-Running Clocks
COUNT 2031 [495] 2032 [496] W1 ENABLED WRITE 2031 [495] W2 2030 [494] W3
[22,27,30]
2031 [495] W4 ENABLED WRITE
2032 [496] W5 ENABLED WRITE
2033 [497] W6 ENABLED WRITE
CKW
ENW tSKEW1 CKR
R1 R2 ENABLED READ
tSKEW2
R3 ENABLED READ R4 R5 R6
ENR HF
LOW
E/F
HIGH
tFD PAFE
tFD
tFD
C451-17
Notes: 35. W2 updates the flag to the Almost Full state by asserting PAFE. Because R1 occurs greater than t SKEW1 after W2, W2 does not recognize R1 when updating the flag status. W3 includes R2 in the flag update because R2 occurs greater than tSKEW2 before W3. Note that W3 does not have to be enabled to update flags. 36. The dashed lines show W3 as a flag update write rather than an enabled write because ENW is deasserted.
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Switching Waveforms (continued)
Write to Almost Full Timing Diagram with Write Flag Update Cycle and Free-Running Clocks
2030 (no change) [494] COUNT 2031 [495] 2032 [496] W1 ENABLED WRITE 2031 [495] W2 2030 [494] W3 FLAG UPDATE CYCLE 2031 [495] W5 ENABLED WRITE 2032 [496] W6 ENABLED WRITE 2033 [497] W7 ENABLED WRITE
[22,27,30]
CKW
W4 FLAG UPDATE WRITE
ENW tSKEW1 CKR
R1 R2 ENABLED READ
tSKEW2
R3 ENABLED READ R4 R5 R6 R7
ENR
LOW HIGH
HF E/F
tFD PAFE
tFD
tFD
C451-19
Write to Full Flag Timing Diagram with Free-Running Clocks
COUNT 2047 [511] 2048 [512] W1 ENABLED WRITE W2 IGNORED WRITE 2047 [511] W3 IGNORED WRITE
[22,23,30,37]
LATENT CYCLE 2048 [512] W5 ENABLED WRITE W6 IGNORED WRITE
CKW
tSKEW2 ENW tSKEW1 CKR
R1 R2 R3 ENABLED READ
W4 FLAG UPDATE WRITE
tSKEW2
R4 R5 R6
ENR
LOW
HF
tFD E/F
LOW
tFD
tFD
PAFE
C451-20
Notes: 37. W2 is ignored because the FIFO is full (count = 4096[2048,512]). It is important to note that W3 is also ignored because R3, the first enabled read after full, occurs less than tSKEW2 before W3. Therefore, the FIFO still appears full when W3 occurs. Because R3 occurs greater than t SKEW2 before W4, W4 includes R3 in the flag update.
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
Switching Waveforms (continued)
Even Parity Generation Timing Diagram
CKR
[38,39]
ENABLED READ
DISABLED READ
tPG Q8/PG/PE
Q0- 7
PREVIOUS WORD: EVEN NUMBER OF 1s
NEW WORD ODD NUMBER OF 1s
ENR
C451-21
[38,40]
Even Parity Generation Timing Diagram
CKR
ENABLED READ DISABLED READ
tPG Q8/PG/PE
Q0- 7
PREVIOUS WORD: ODD NUMBER OF 1s
NEW WORD EVEN NUMBER OF 1s
ENR
C451-22
Notes: 38. In this example, the FIFO is assumed to be programmed to generate even parity. 39. If Q0 - 7 "new word" also has an even number of 1s, then PG stays LOW. 40. If Q0 - 7 "new word" also has an odd number of 1s, then PG stays HIGH.
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
Switching Waveforms (continued)
Even Parity Checking [41]
CKW
WRITE M WRITE M+1 WRITE M+2
ENW
D0- 8
WORD M: EVEN NUMBER OF "1"s
WORD M+ 1: ODD NUMBER OF "1"s
WORD M+ 2: EVEN NUMBER OF "1"s
CKR
READ M
READ M+1
READ M+2
ENR tPE F1 Q8/PG/ PE tPE
Q0- 7
[42,43]
8 LSBs OF WORD M-1
8 LSBs OF WORD M
8 LSBs OF WORD M+1
8 LSBs OF WORD M+2 C451-23
Output Enable Timing
CKR
READ M+1
ENR
LOW
OE tOHZ Q0- 8
VALID DA TA WORD M
tOE
VALID DA TA WORD M+1
tOLZ
C451-24
Retransmit Timing[44, 45]
FL/RT tPRT tRTR ENR/ENW
E/F,HF,PAFE
C451-25
Notes: 41. In this example, the FIFO is assumed to be programmed to check for even parity. 42. This example assumes that the time from the CKR rising edge to valid word M+1 > tA. 43. If ENR was HIGH around the rising edge of CKR (i.e., read disabled), the valid data at the far right would once again be word M instead of word M+1. 44. Clocks are free running in this case. 45. 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.
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
Architecture
The CY7C451, CY7C453, and CY7C454 consist of an array of 512/2048/4096 words of 9 bits each (implemented by an array of dual-port RAM cells), a read pointer, a write pointer, control signals (CKR, CKW, ENR, ENW, MR, OE, FL/RT, XI, XO), and flags (HF, E/F, PAFE). of tFTP after a program write, and the program word will be available tAP after the read occurs. If a program write does not occur, a program read may occur a minimum of tSMRP after MR is asserted. This will read the default program value. When free-running clocks are tied to CKW and CKR, programming can still occur during a master reset cycle with the adherence to a few additional timing parameters. The enable pins must be set-up tSEN before the rising edge of CKW or CKR. Hold times of tHEN must also be met for ENW and ENR. Data present on D0 - 5 during a program write will determine the distance from Empty (Full) that the Almost Empty (Almost Full) flags will become active. See Table 1 for a description of the six possible FIFO states. P in 1 refers to the decimal equivalent of the binary number represented by D0 - 5. Programming options for the CY7C451 and CY7C453 are listed in Table 5. Programming resolution is 16 words for either device. The programmable PAFE function is only valid when the CY7C451/453/454 are not cascaded. If the user elects not to program the FIFO's flags, the default (P=1) is as follows: Almost Empty condition (Almost Full condition) is activated when the CY7C451/453/454 contain 16 or less words (empty locations). Parity is programmed with the D6 - 8 bits. See Table 6 for a summary of the various parity programming options. Data present on D6 - 8 during a program write will determine whether the FIFO will generate or check even/odd parity for the data present on D0-8 thereafter. If the user elects not to program the FIFO, the parity function is disabled. Flag operation and parity are described in greater detail in subsequent sections.
Resetting the FIFO
Upon power-up, the FIFO must be reset with a Master Reset (MR) cycle. This causes the FIFO to enter the Empty condition signified by E/F and PAFE being LOW and HF being HIGH. All data outputs (Q0 - 8) go low at the rising edge of MR. In order for the FIFO to reset to its default state, a falling edge must occur on MR and the user must not read or write while MR is LOW (unless ENR and ENW are HIGH or unless the device is being programmed). Upon completion of the Master Reset cycle, all data outputs will go LOW tAMR after MR is deasserted. All flags are guaranteed to be valid tMRF after MR is taken HIGH.
FIFO Operation
When the ENW signal is active (LOW), data present on the D0 - 8 pins is written into the FIFO on each rising edge of the CKW signal. Similarly, when the ENR signal is active, data in the FIFO memory will be presented on the Q0 - 8 outputs. New data will be presented on each rising edge of CKR while ENR is active. ENR must be set up t SEN before CKR for it to be a valid read function. ENW must occur tSEN before CKW for it to be a valid write function. An output enable (OE) pin is provided to tri-state the Q0 - 8 outputs when OE is not asserted. When OE is enabled, data in the output register will be available to Q0 - 8 outputs after tOE. If devices are cascaded, the OE function will only output data on the FIFO that is read enabled. The FIFO contains overflow circuitry to disallow additional writes when the FIFO is full, and underflow circuitry to disallow additional reads when the FIFO is empty. An empty FIFO maintains the data of the last valid read on its Q0 - 8 outputs even after additional reads occur.
Flag Operation
The CY7C451/453/454 provide three status pins when not cascaded. The three pins, E/F, PAFE, and HF, allow decoding of six FIFO states (Table 1). PAFE is not available when FIFOs are cascaded for depth expansion. All flags are synchronous, meaning that the change of states is relative to one of the clocks (CKR or CKW, as appropriate. See Figure 1). The synchronous architecture guarantees some minimum valid time for the flags. The Empty and Almost Empty flag states are exclusively updated by each rising edge of the read clock (CKR). For example, when the FIFO contains 1 word, the next read (rising edge of CKR while ENR=LOW) causes the flag pins to output a state that represents Empty. The Half Full, Almost Full, and Full flag states are updated exclusively by the write clock (CKW). For example, if the CY7C453 FIFO contains 2047 words (2048 words indicate Full for the CY7C453), the next write (rising edge of CKW while ENW=LOW) causes the flag pins to output a state that is decoded as Full.
]
Programming
The CY7C451, CY7C453, and CY7C454 are programmed during a master reset cycle. If MR and ENW are LOW, a rising edge on CKW will write D0 - 8 inputs into the programming register. MR must be set up a minimum of tSMRP before the program write rising edge and held tHMRP after the program write falling edge. The user has the ability to also perform a program read during the master reset cycle. This will occur at the rising edge of CKR when MR and ENR are asserted. The program read must be performed a minimum Table 1. Flag Truth Table[46].
E/F 0 1 1
PAFE 0 0 1
HF 1 1 1
State Empty Almost Empty Less than or Equal to Half Full
CY7C451 512 x 9 Number of Words in FIFO 0 1(16*P) (16*P)+1256
CY7C453 2K x 9 Number of Words in FIFO 0 1 (16*P) (16*P)+11024
CY7C454 4K x 9 Number of Words in FIFO 0 1 (16*P) (16*P)+12048
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
Table 1. Flag Truth Table[46]. CY7C451 512 x 9 Number of Words in FIFO 257511-(16*P) 512- (16*P) 511 512 CY7C453 2K x 9 Number of Words in FIFO 10252047-(16*P) CY7C454 4K x 9 Number of Words in FIFO 2049 4095-(16*P)
E/F 1 1 0
PAFE 1 0 0
HF 0 0 0
State Greater than Half Full Almost Full Full
2048-(16*P) 2047 4096-(16*P) 4095 2048 4096
Notes: 46. P is the decimal value of the binary number represented by D0 - 5. When programming the CY7C451/453/454, P can have values from 0 to 15 for the CY7C451 and values from 0 to 63 for the CY7C453 and CY7C454. See Table 5 for D0 - 5 representation. P = 0 signifies Almost Empty state = Empty state.
E CKR
DQ
dates the flag. If a write occurs at least tSKEW2 before a read, the write is guaranteed to be included when CKR updates flag. If a write occurs within tSKEW1/tSKEW2 after or before CKR, then the decision of whether or not to include the write when the flag is updated by CKR is arbitrary.
E/F
F CKW
DQ
The update cycle for non-boundary flags (Almost Empty, Half Full, Almost Full) is different from that used to update the boundary flags (Empty, Full). Both operations are described below.
Boundary and Non-Boundary Flags
PAE CKR PAFE PAF CKW DQ DQ
Boundary Flags (Empty) The Empty flag is synchronized to the CKR signal (i.e., the Empty flag can only be updated by a clock pulse on the CKR pin). An empty FIFO that is written to will be described with an Empty flag state until a rising edge is presented to the CKR pin. When making the transition from Empty to Almost Empty (or Empty to Less than or Equal to Half Full), a clock cycle on the CKR is necessary to update the flags to the current state. In such a state (flags showing Empty even though data has been written to the FIFO), two read cycles are required to read data out of FIFO. The first read serves only to update the flags to the Almost Empty or Less than or Equal to Half Full state, while the second read outputs the data. This first read cycle is known as the latent or flag update cycle because it does not affect the data in the FIFO or the count (number of words in FIFO). It simply deasserts the Empty flag. The flag is updated regardless of the ENR state. Therefore, the update occurs even when ENR is unasserted (HIGH), so that a valid read is not necessary to update the flags to correctly describe the FIFO. In this example, the write must occur at least tSKEW2 before the flag update cycle in order for the FIFO to guarantee that the write will be included in the count when CKR updates the flags. When a free-running clock is connected to CKR, the flag is updated each cycle. Table 2 shows an example of a sequence of operations that update the Empty flag. Boundary Flags (Full) The Full flag is synchronized to the CKW signal (i.e., the Full flag can only be updated by a clock pulse on the CKW pin). A full FIFO that is read will be described with a Full flag until a rising edge is presented to the CKW pin. When making the transition from Full to Almost Full (or Full to Greater Than Half Full), a clock cycle on the CKW is necessary to update the flags to the current state. In such a state (flags showing Full even through data has been read from the FIFO), two write cycles are required to write data into the FIFO. The first write serves only to update the flags to the Almost Full or Greater
HF CKW
DQ HF INTERNAL LOGIC PIN
Figure 1. Flag Logic Diagram.
Flag Operation (continued)
Since the flags denoting emptiness (Empty, Almost Empty) are only updated by CKR and the flags signifying fullness (Half Full, Almost Full, Full) are exclusively updated by CKW, careful attention must be given to the flag operation. The user must be aware that if a boundary (Empty, Almost Empty, Half Full, Almost Full, or Full) is crossed due to an operation from a clock that the flag is not synchronized to (i.e., CKW does not affect Empty or Almost Empty), a flag update cycle is necessary to represent the FIFO's new state. The signal to which a flag is not synchronized will be referred to as the opposite clock (CKW is opposite clock for Empty and Almost Empty flags; CKR is the opposite clock for Half Full, Almost Full, and Full flags). Until a proper flag update cycle is executed, the synchronous flags will not show the new state of the FIFO. When updating flags, the CY7C451/453/454 must make a decision as to whether or not the opposite clock was recognized when a clock updates the flag. For example (when updating the Empty flag), if a write occurs at least tSKEW1 after a read, the write is guaranteed not to be included when CKR up-
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
Than Half Full state, while the second write inputs the data. This first write cycle is known as the latent or flag update cycle because it does not affect the data in the FIFO or the count (number of words in the FIFO). It simply deasserts the Full flag. The flag is updated regardless of the ENW state. Therefore, the update occurs even when ENW is deasserted (HIGH), so that a valid write is not necessary to update the flags to correctly describe the FIFO. In this example, the read must occur at least tSKEW2 before the flag update cycle in order for the FIFO to guarantee that the read will be included in the count when CKW updates the flags. When a free-running clock is connected to CKW, the flag updates each cycle. Full flag operation is similar to the Empty flag operation described in Table 2. Non-Boundary Flags (Almost Empty, Half Full, Almost Full) The CY7C451/453/454 feature programmable Almost Empty and Almost Full flags. Each flag can be programmed a specific distance from the corresponding boundary flags (Empty or Full). The flags can be programmed to be activated at the Empty or Full boundary, or at a distance of up to 1008 words/locations for the CY7C453 and CY7C454 (240 words/locations for the CY7C451) from the Empty/Full boundary. The programming resolution is 16 words/locations. When the FIFO contains the number of words or fewer for which the flags have been programmed, the PAFE flag will be asserted signifying that the FIFO is Almost Empty. When the FIFO is within that same number of empty locations from being Full, the PAFE will also be asserted signifying that the FIFO is Almost Full. The HF flag is decoded to distinguish the states. The default distance (CY7C451/453/454 not programmed) from where PAFE becomes active to the boundary (Empty, Table 2. Empty Flag (Boundary Flag) Operation Example. Status Before Operation Current Number State of of Words FIFO E/F AFE HF in FIFO Empty 0 0 1 0 Empty Empty AE AE Empty Empty AE 0 0 1 1 0 1 1 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 2 2 1 0 1 1 Status After Operation Next Number State of words of FIFO E/F AFE HF in FIFO Empty 0 0 1 1 Empty AE AE Empty Empty AE Empty 0 1 1 0 0 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 2 2 1 0 1 1 0 Full) is 16 words/locations. The Almost Full and Almost Empty flags can be programmed so that they are only active at Full and Empty boundaries. However, the operation will remain consistent with the non-boundary flag operation that is discussed below. Almost Empty is only updated by CKR while Half Full and Almost Full are updated by CKW. Non-boundary flags employ flag update cycles similar to the boundary flag latent cycles in order to update the FIFO status. For example, if the FIFO just reaches the Greater than Half Full state, and then two words are read from the FIFO, a write clock (CKW) will be required to update the flags to the Less than Half Full state. However, unlike the boundary flag latent cycle, the state of the enable pin (ENW in this case) affects the operation. Therefore, set-up and hold times for the enable pins must be met (tSEN and tHEN). If the enable pin is active during the flag update cycle, the count and data are updated in addition to PAFE and HF. If the enable pin is not asserted during the flag update cycle, only the flags are updated. Table 3 and Table 4 show an example of a sequence of operations that update the Almost Empty and Almost Full flags.
Programmable Parity
The CY7C451/453/454 also features even or odd parity checking and generation. D6 - 8 are used during a program write to describe the parity option desired. Table 6 gives a summary of programmable parity options. If the user elects not to program the device, then parity is disabled. Parity information is provided on one multi-mode output pin (Q8/PG/PE). The three possible modes are described in the following paragraphs. Regardless of the mode selected, the OE pin retains three-state control of all 9 Q 0 - 8 bits.
Operation Write (ENW = 0) Write (ENW = 0) Read (ENR = X) Read (ENR = 0) Read (ENR = 0) Write (ENR = 0) Read (ENR = X) Read (ENR = 0)
Comments Write Write Flag Update Read Read (transition from Almost Empty to Empty) Write Flag Update Read (transition from Almost Empty to Empty)
Parity Disabled (Q8 mode) When parity is disabled (or user does not program parity option) the CY7C451/453/454 stores all 9 bits present on D0 - 8 inputs internally and will output all 9 bits on Q0 - 8 Parity Generate (PG mode). Document #: 38-06033 Rev. *A
This mode is used to generate either even or odd parity (as programmed) from D0 - 7. D8 input is ignored. The parity bit is stored internally as D8 and during a subsequent read will be available on the PG pin along with the data word from which the parity was generated (Q 0 - 7). For example, if
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CY7C451 CY7C453 CY7C454
parity generate is set to ODD and the D 0 - 7 inputs have an EVEN number of 1s, PG will be HIGH. Parity Check (PE mode) If the CY7C451/453/454 is programmed for parity checking, the FIFO will compare the parity of D0 - 8 with the program register. If the expected parity is present, D8 will be set HIGH internally. When this word is later read, PE will be HIGH. If a parity error occurs, D8 will be set LOW internally. When this word is later read, PE will be LOW. For example, if parity check is set to odd and D0 - 8 have an even number of 1s, a parity error occurs. When that word is later read, PE will be asserted (LOW). 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 standalone 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 since the last MR cycle. A LOW 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. occur when the first write to an empty FIFO and a read are very close together. If the read occurs less than tSKEW2 after the first write to two width-expanded devices, A and B, device A may go Almost Empty (read recognized as flag update) while device B stays Empty (read ignored). This occurs because a read can be either recognized or ignored if it occurs within tSKEW2 of a write. The next read cycle outputs the first half of the first word on device A while device B updates its flags to Almost Empty. Subsequent reads will continue to output "staggered" data assuming more data has been written to the FIFOs.
Depth Expansion Mode
The CY7C451/453/454 can operate up to 83.3 MHz when cascaded. Depth expansion is accomplished by connecting expansion out (XO) of the first device to expansion in (XI) of the next device, with XO of the last device connected to XI of the first device. The first device has its first load pin (FL) tied to VSS while all other devices must have this pin tied to VCC. The first device will be the first to be write and read enabled after a master reset. Proper operation also requires that all cascaded devices have common CKW, CKR, ENW, ENR, D0 - 8, Q0 - 8, and MR pins. When cascaded, one device at a time will be read enabled so as to avoid bus contention. By asserting XO when appropriate, the currently enabled FIFO alerts the next FIFO that it should be enabled. The next rising edge on CKR puts Q0 - 8 outputs of the first device into a high-impedance state. This occurs regardless of the state of ENR or the next FIFO's Empty flag. Therefore, if the next FIFO is empty or undergoing a latent cycle, the Q0 - 8 bus will be in a high-impedance state until the next device receives its first read, which brings its data to the Q0 - 8 bus.
Width Expansion Modes
During width expansion all flags (programmable and nonprogrammable) are available. The CY7C451/453/454 can be expanded in width to provide word width greater than nine in increments of nine. During width expansion mode all control line inputs are common. When the FIFO is being read near the Empty (Full) boundary, it is important to note that both sets of flags should be checked to see if they have been updated to the Not Empty (Not Full) condition to insure that the next read (write) will perform the same operation on all devices. Checking all sets of flags is critical so that data is not read from the FIFOs "staggered" by one clock cycle. This situation could
Program Write/Read of Cascaded Devices
Programming of cascaded FIFOs is the same as for a single device. Because the controls of the FIFOs are in parallel when cascaded, they all get programmed the same. During program mode, only parity is programmed since Almost Full and Almost Empty flags are not available when CY7C451/453/454 are cascaded. Only the "first device" (FIFO with FL=LOW) will output its program register contents on Q0 - 8 during a program read. Q0 - 8 of all other devices will remain in a high-impedance state to avoid bus contention.
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
CKW ENW XI D0 - 8 Q0 - 8
CKR ENR
CKW CKR CY7C451/3/4 ENW ENR MR DATA IN D0- 8 MR OE XI D0 - 8 CKW Q0 - 8 CKR OE HF E/F FL/RT PAFE/XO DATA OUT Q0- 8 VSS
ENW ENR CY7C451/3/4 HF MR OE E/F FL/RT PAFE/XO
FULL
EMPTY
VCC
Figure 2. Depth Expansion with CY7C451/3/4. Table 3. Almost Empty Flag (Non-Boundary Flag) Operation Example[47] . Status Before Operation Current State of FIFO AE AE AE E/F 1 1 1 1 1
AFE 0 0 0 1 1
HF 1 1 1 1 1
Operation Write (ENW = 0) Write (ENW = 0) Read (ENR = 0) Read (ENR = 1) Read (ENR = 0)
E/F 1 1 1 1 1
PAFE 0 0 1 1 0
HF 1 1 1 1 1
Comments
Notes: 47. Applies to both CY7C451, CY7C453, and CY7C454 operations when devices are programmed so that Almost Empty becomes active when the FIFO contains 32 or fewer words.
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
.]
Table 4. Almost Full Flag Operation Example[48] . Number of Words in FIFO CY7C451 496 495 495 494 494 494 494 495 495 496 Number of Words in FIFO CY7C453 2032 2031 2031 2030 2030 2030 2030 2031 2031 2032 Number of Words in FIFO CY7C454 4080 4079 4079 4078 4078 4078 4078 4079 4079 4080 Write (Transition from >HF to AF) Write Flag Update Read
Operation Read (ENR=0) Read (ENR=0) Write (ENW=1) Write (ENW=0) Write (ENW =0) Current Next Current Next Current Next Current Next Current Next
State of FIFO AF AF AF AF AF AF >HF >HF >HF >HF
E/F 1 1 1 1 1 1 1 1 1 1
PAFE 0 0 0 0 0 1 1 1 1 0
HF 0 0 0 0 0 0 0 0 0 0
Comments Read
Table 5. Programmable Almost Full/Almost Empty Options - CY7C451/CY7C453/CY7C454[49] . D5 0 0 0 0 D4 0 0 0 0 D3 0 0 0 0 D2 0 0 0 0 D1 0 0 1 1 D0 0 1 0 1 PAFE Active when CY7C451/453/454 is: Completely Full and Empty. 16 or less locations from Empty/Full (default) 32 or less locations from Empty/Full 48 or less locations from Empty/Full P[50] 0 1 2 3
. . .
0 0
. . .
0 0
. . .
1 1
. . .
1 1
. . .
1 1
. . .
0 1
. . .
224 or less locations from Empty/Full 240 or less locations from Empty/Full
. . .
14 15
. . .
1 1
. . .
1 1
. . .
1 1
. . .
1 1
. . .
1 1 0 1
. . .
. . .
992 or less locations from Empty/Full 1008 or less locations from Empty/Full
. . .
62 63
Table 6. Programmable Parity Options. D8 0 1 1 1 1 D7 X 0 0 1 1 D6 X 0 1 0 1 Parity disabled. Generate even parity on PG output pin. Generate odd parity on PG output pin. Check for even parity. Indicate error on PE output pin. Check for odd parity. Indicate error on PE output pin. Condition
Notes: 48. Programmed so that Almost Full becomes active when the FIFO contains 16 or less empty locations. 49. D4 and D5 are don't care for CY7C451. 50. Referenced in Table 1.
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
Ordering Information
512x9 Clocked FIFO Speed (ns) 12 14 20 30 Ordering Code CY7C451-12JC CY7C451-12JI CY7C451-14JC CY7C451-14JI CY7C451-20JC CY7C451-20JI CY7C451-30JC CY7C451-30JI 2Kx9 Clocked FIFO Speed (ns) 12 14 20 30 Ordering Code CY7C453-12JC CY7C453-12JI CY7C453-14JC CY7C453-14JI CY7C453-20JC CY7C453-20JI CY7C453-30JC CY7C453-30JI 4Kx9 Clocked FIFO Speed (ns) 12 14 20 30 Ordering Code CY7C454-12JC CY7C454-12JI CY7C454-14JC CY7C454-14JI CY7C454-20JC CY7C454-20JI CY7C454-30JC CY7C454-30JI Package Name J65 J65 J65 J65 J65 J65 J65 J65 Package Type 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier Operating Range Commercial Industrial Commercial Industrial Commercial Industrial Commercial Industrial Package Name J65 J65 J65 J65 J65 J65 J65 J65 Package Type 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier Operating Range Commercial Industrial Commercial Industrial Commercial Industrial Commercial Industrial Package Name J65 J65 J65 J65 J65 J65 J65 J65 Package Type 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier 32-Lead Plastic Leaded Chip Carrier Operating Range Commercial Industrial Commercial Industrial Commercial Industrial Commercial Industrial
Document #: 38-06033 Rev. *A
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CY7C451 CY7C453 CY7C454
Package Diagram
32-Lead Plastic Leaded Chip Carrier J65
Document #: 38-06033 Rev. *A
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(c) Cypress Semiconductor Corporation, 2001. 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 Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor 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 Semiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.
CY7C451 CY7C453 CY7C454
Document Title: CY7C451, CY7C453, CY7C454 512 x 9, 2K x 9, and 4K x 9, Cascadable Clocked FIFOs with Programmable Flags Document Number: 38-06033 REV. ** *A ECN NO. 110174 122284 Issue Date 09/29/01 12/27/02 Orig. of Change SZV RBI Description of Change Change from Spec number: 38-00125 to 38-06033 Power up requirements added to Maximum Ratings Information
Document #: 38-06033 Rev. *A
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