CY7C4255V_02 Datasheet, PDF (11/20 Pages) Cypress Semiconductor – 32K/64Kx18 Low Voltage Deep Sync FIFOs

CY7C4255V/CY7C4265V
CY7C4275V/CY7C4285V
Switching Waveforms (continued)
Programmable Almost Empty Flag Timing (applies only in SMODE (SMODE is LOW))
t_CLKH
t_CLKL
WCLK
WEN
t_ENS t_ENH
PAE
RCLK
REN
t_SKEW3 ^[22]
Note ²¹
t_{PAE synch}
N + 1 WORDS
IN FIFO
t_ENS
t_ENS t_ENH
Note 23 _{tPAE synch}
Programmable Almost Full Flag Timing
4275V–16
WCLK
WEN
t_CLKH
Note 24
t_CLKL
t_ENS t_ENH
[25]
PAF
RCLK
REN
t_PAF
FULL– M WORDS
IN FIFO^[26]
FULL– (M+1) WORDS
IN FIFO ^[27]
t_PAF
t_ENS
4275V–17
Notes:
21. PAE offset − n.
22. t_SKEW3 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 t_SKEW3, then PAE may not change state until the next RCLK.
23. If a read is performed 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 CY7C4255V, 16384 − (m + 1) for the CY7C4265V, 32768 − (m +
1) for the CY7C4275V, and 65536 − (m + 1) for the CY7C4285V.
25. PAF is offset = m.
26. 8192 − m words in CY7C4255V, 16384 − m words in CY7C4265V, 32768 − m words in CY7C4275V, and 65536 − m words in CY7C4285V.
27. 8192 − (m + 1) words in CY7C4255V, 16384 − (m + 1) words in CY7C4265V, 32768 − (m + 1) words in CY7C4275V, and 65536 − (m + 1) words in CY7C4285V.
Document #: 38-06012 Rev. *A
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