CY7C4421/4201/4211/4221
CY7C4231/4241/4251
Switching Waveforms
(continued)
Programmable Almost Full Flag Timing
t
CLKH
WCLK
t
ENS
t
ENH
WEN1
Note
t
ENS
t
ENH
PAF
FULL
−
M+1 WORDS
IN FIFO
t
PAF
FULL
−
M WORDS
IN FIFO
t
SKEW2
t
PAF
t
CLKL
Note
WEN2
(if applicable)
RCLK
t
ENS
REN1,
REN2
t
ENS
t
ENH
Write Programmable Registers
t
CLK
t
CLKH
WCLK
t
ENS
WEN2/LD
t
ENS
WEN1
t
DS
D
0
–D
8
PAE OFFSET
LSB
PAE OFFSET
MSB
PAF OFFSET
LSB
PAF OFFSET
MSB
t
DH
t
ENH
t
CLKL
Notes:
21. t
SKEW2
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
SKEW2
, 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. t
SKEW2
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 t
SKEW2
, then PAF may not change state until the next WCLK.
Document #: 38-06016 Rev. *A
Page 12 of 18
CYPRESS [ CYPRESS SEMICONDUCTOR ]
