13 / 19 page
CY7C4421/4201/4211/4221
CY7C4231/4241/4251
Document #: 38-06016 Rev. *C
Page 13 of 19
Programmable Almost Full Flag Timing
Write Programmable Registers
Notes:
25. 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.
26. PAF offset = m.
27. 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.
28. 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.
Switching Waveforms (continued)
tENH
WCLK
PAF
RCLK
tCLKH
tENS
FULL
− M WORDS
IN FIFO
tCLKL
tENS
FULL
− M+1 WORDS
IN FIFO
tENH
tENS
tENH
tENS
tPAF
REN1,
REN2
WEN1
WEN2
(if applicable)
tSKEW2
tPAF
Note
25
Note
26
[27]
[28]
tENH
WEN2/LD
WCLK
tCLKH
tENS
tCLKL
PAE OFFSET
LSB
D0 –D8
WEN1
tENS
PAF OFFSET
MSB
tCLK
tDS
tDH
PAE OFFSET
MSB
PAF OFFSET
LSB
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