Switching Waveforms (continued)
Programmable Almost Empty Flag Timing (applies only in SMODE (SMODE is LOW))
tCLKH
tCLKL
WCLK
WEN
tENS tENH
PAE
RCLK
REN
tSKEW3 [22]
Note 21
tPAE synch
N + 1 WORDS
IN FIFO
tENS
tENS tENH
CY7C4275
CY7C4285
Note 23 tPAE synch
Programmable Almost Full Flag Timing
4275–14
WCLK
WEN
tCLKH
Note 24
tCLKL
tENS tENH
PAF [25]
RCLK
REN
tPAF
FULL– M WORDS
IN FIFO[26]
FULL– (M+1) WORDS
IN FIFO [27]
tPAF
tENS
4275–15
Notes:
21. PAE offset − n.
22. tSKEW3 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 tSKEW3, then PAE may not change state until the next RCLK.
23. If a read is preformed 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 = 32768 − (m + 1) for the CY7C4285 and 65536 − (m + 1) for the CY7C4285.
25. PAF is offset = m.
26. 32768 − m words in CY7C4275 and 65536 – m words in CY7C4285.
27. 32768 − (m + 1) words in CY7C4275 and 65536 – (m + 1) CY7C4285.
Document #: 38-06008 Rev. *A
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