CY7C4801/4811/4821
CY7C4831/4841/4851
Flag Operation
(FFA,FFB) is synchronized to (WCLKA,WCLKB), i.e., it is exclusively
updated by each rising edge of (WCLKA,WCLKB).
The CY7C48X1 devices provide four flag pins to indicate the
condition of the FIFO contents. Empty, Full, (PAEA,PAEB), and
(PAFA,PAFB) are synchronous.
Empty Flag
The Empty Flag (EFA,EFB) will go LOW when the device is empty.
Read operations are inhibited whenever (EFA,EFB) is LOW, regard-
less of the state of (RENA1,RENB1) and (RENA2,RENB2.
(EFA,EFB) is synchronized to (RCLKA,RCLKB), i.e., it is exclusively
Full Flag.
Full Flag
The Full Flag (FFA,FFB) will go LOW when the device is full. Write
operations are inhibited whenever (FFA,FFB) is LOW regardless of
the state of (WENA1,WENB1) and (WENA2/LDA,WENB2/LDB).
Table 2. Status Flags.
Number of Words in FIFO
CY7C4801
CY7C4811
CY7C4821
FF
H
H
H
H
L
PAF
H
PAE
L
EF
L
0
0
0
1 to n[25]
1 to n[25]
1 to n[25]
H
L
H
H
H
H
(n+1) to (256-(m+1))
(256−m)[26] to 255
256
(n+1) to (512-(m+1))
(512−m)[26] to 511
512
(n+1) to (1024 −(m+1))
(1024−m)[26] to 1023
1024
H
H
L
H
L
H
Number of Words in FIFO
CY7C4841
CY7C4831
CY7C4851
FF PAF PAE EF
0
0
0
H
H
H
H
L
H
H
H
L
L
L
L
1 to n[25]
1 to n[25]
1 to n[25]
H
H
H
H
(n+1) to (2048 −(m+1)) (n+1) to (4096 −(m+1)) (n+1) to (8192 −(m+1))
H
H
H
(2048−m)[26] to 2047
(4096−m)[26] to 4095
(8192−m)[26] to 8191
2048
4096
8192
L
Notes:
25. n =Empty Offset (n=7 default value).
26. m = Full Offset (m=7 default value).
Document #: 38-06005 Rev. **
Page 16 of 23
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