CY7C4425/4205/4215
CY7C4225/4235/4245
Switching Waveforms
(continued)
Programmable Almost Full Flag Timing
t
CLKH
Note 23
WCLK
t
ENS
t
ENH
WEN
t
PAF
PAF
[24]
t
CLKL
FULL
−
M WORDS
IN FIFO
[25]
t
PAF
FULL
−
M + 1 WORDS
IN FIFO
[26]
RCLK
t
ENS
REN
42X5–15
Programmable Almost Full Flag Timing (applies only in SMODE (SMODE in LOW))
t
CLKH
WCLK
t
ENS
t
ENH
WEN
t
CLKL
Note
27
WEN2
t
ENS
t
ENH
PAF
FULL- M+1Ω ORDS
INFIFO
Note
28
t
PAF
FULL
−
M WORDS
[29]
IN FIFO
[30]
t
SKEW3
t
PAFsynch
RCLK
t
ENS
REN
42X5–16
t
ENS
t
ENH
Notes:
23. PAF offset = m. Number of data words written into FIFO already = 64 – m + 1 for the CY7C4425, 256 – m + 1 for the CY7C4205, 512 – m + 1 for the
CY7C4215. 1024 – m + 1 for the CY7C4225, 2048 – m + 1 for the CY7C4235, and 4096 – m + 1 for the CY7C4245.
24. PAF is offset = m.
25. 64 – m words in CY7C4425, 256 – m words inCY7C4205, 512 – m word in CY7C4215. 1024 – m words in CY7C4225, 2048 – m words in CY7C4235, and
4096 – m words in CY7C4245.
26. 64 – m + 1 words in CY7C4425, 256 – m + 1 words in CY7C4205, 512 – m +1 words in CY7C4215, 1024 – m + 1 CY7C4225, 2048 – m + 1 in CY74235,
and 4096 – m + 1 words in CY7C4245.
27. If a write is performed on this rising edge of the write clock, there will be Full – (m – 1) words of the FIFO when PAF goes LOW.
28. PAF offset = m.
29. 64 – m words in CY7C4425, 256 – m words in FIFO for CY7C4205, 512 – m word in CY7C4215. 1024 – m words in CY7C4225, 2048 – m words in CY7C4235,
and 4096 – m words in CY7C4245.
30. t
SKEW3
is the minimum time between a rising RCLK and a rising WCLK edge for PAF to change state during that clock cycle. If the time between the edge of RCLK and the
rising edge of WCLK is less than t
SKEW3
, then PAF may not change state until the next WCLK rising edge.
11
CYPRESS [ CYPRESS SEMICONDUCTOR ]
