CY7C4421/4201/4211/4221
CY7C4231/4241/4251
Switching Waveforms (continued)
Programmable Almost Full FlagTiming
Note
24
t
t
CLKL
CLKH
WCLK
t
t
t
ENS
ENH
WEN1
Note
25
WEN2
(if applicable)
t
t
PAF
ENS
ENH
FULL − M WORDS
PAF
[26]
IN FIFO
FULL − M+1 WORDS
IN FIFO
[27]
t
t
PAF
SKEW2
RCLK
t
ENS
t
t
ENH
ENS
REN1,
REN2
Write Programmable Registers
t
CLK
t
t
CLKL
CLKH
WCLK
t
t
ENS
ENH
WEN2/LD
t
ENS
WEN1
t
t
DH
DS
D –D
0
8
PAE OFFSET
LSB
PAE OFFSET
MSB
PAF OFFSET
LSB
PAF OFFSET
MSB
Notes:
21. tSKEW2 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 tSKEW2, then PAE may not change state until the next RCLK.
22. PAE offset = n.
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. 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.
25. PAF offset = m.
26. 64-m words for CY7C4421, 256 – m words in FIFO for CY7C4201, 512 – m words for CY7C4211, 1024 – m words for CY7C4221, 2048 – m words for CY7C4231,
4096 – m words for CY7C4241, 8192 – m words for CY7C4251.
27. tSKEW2 is the minimum time between a rising RCLK edge and a rising WCLK edge for PAF to change during that clock cycle. If the time between the rising
edge of RCLK and the rising edge of WCLK is less than tSKEW2, then PAF may not change state until the next WCLK.
Document #: 38-06016 Rev. *A
Page 12 of 18
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