CY7C456-30JI 参数 Datasheet PDF下载

CY7C455

CY7C456

CY7C457

Switching Waveforms

(continued)

Write to Almost Full Timing Diagram

COUNT

2030

[1016]

[494]

2031

[1017]

[495]

2032

[1018]

[496]

[21, 26, 29, 34, 35]

2031

[1017]

[495]

2030

[1016]

[494]

2031 [1017]

[495]

2030 [1016]

[494]

W3

ENABLED

WRITE

FLAG UPDATE

2032

[496]

2031 [1017]

[495]

W4

ENABLED

WRITE

2033

[497]

2032 [1018]

[496]

W5

ENABLED

WRITE

CKW

W1

ENABLED

WRITE

W2

ENABLED

WRITE

ENW

LOW

t

SKEW1

CKR

ENR

LOW

R1

ENABLED

READ

R2

ENABLED

READ

t

SKEW2

t

FD

PAFE

HF

E/F

LOW

t

FD

t

FD

t

FD

HIGH

c455-18

Write to Almost Full Timing Diagram with Free-RunningClocks

COUNT

2031

[1017]

[495]

2032

[1018]

[496]

W1

ENABLED

WRITE

2031

[1017]

[495]

W2

2030

[1016]

[494]

W3

[21, 26, 29]

2031

[1017]

[495]

W4

ENABLED

WRITE

2032

[1018]

[496]

W5

ENABLED

WRITE

2033

[1019]

[497]

W6

ENABLED

WRITE

CKW

ENW

t

SKEW1

CKR

R1

R2

ENABLED

READ

t

SKEW2

R3

ENABLED

READ

R4

R5

R6

ENR

HF

LOW

E/F

HIGH

t

FD

PAFE

t

FD

t

FD

c455-17

Notes:

34. 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 flag status. W3 includes R2 in the flag update because R2 occurs greater than t

SKEW2

before W3. Note that W3 does not have to be enabled

to update flags.

35. The dashed lines show W3 as a flag update write rather than an enabled write because ENW is HIGH.

Document #: 38-06003 Rev. **

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