CY7C451 Ver la hoja de datos (PDF) - Cypress Semiconductor
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CY7C451 Datasheet PDF : 24 Pages
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CY7C451
CY7C453
CY7C454
Switching Waveforms (continued)
Read to Almost Empty Timing Diagram with Free-Running Clocks [22,25,27]
COUNT
17
16
17
18
17
CKR
R1
R2
ENABLED
READ
R3
R4
ENABLED
READ
ENR
CKW
tSKEW1
W1
W2
ENABLED
WRITE
tSKEW2
W3
W4
ENABLED
WRITE
ENW
HF
HIGH
HIGH
E/F
16
R5
ENABLED
READ
W15
15
R6
ENABLED
READ
W6
tFD
tFD
tFD
PAFE
C451-14
[22,25,27,28,29]
Read to Almost Empty Timing Diagram with Read Flag Cycle and Update Free-Running Clocks
COUNT 17 16
17
18 (no change)
18
FLAG UPDATE CYCLE 17
16
15
CKR
ENR
CKW
R1
ENABLED
READ
tSKEW1
W1
ENW
HIGH
HF
R2
W2
ENABLED
WRITE
R3
R4
FLAG
UPDATE
READ
tSKEW2
W3
W4
ENABLED
WRITE
R5
ENABLED
READ
R6
ENABLED
READ
R7
ENABLED
READ
W5
W6
W7
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.
Document #: 38-06033 Rev. *A
Page 10 of 24
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