CY7C024/024A/0241
CY7C025/0251
Document #: 38-06035 Rev. *D
Page 12 of 21
Notes
28. R/W must be HIGH during all address transitions.
29. A write occurs during the overlap (tSCE or tPWE) of a LOW CE or SEM and a LOW UB or LB.
30. tHA is measured from the earlier of CE or R/W or (SEM or R/W) going HIGH at the end of write cycle.
31. If OE is LOW during a R/W controlled write cycle, the write pulse width must be the larger of tPWE or (tHZWE + tSD) to allow the I/O drivers to turn off and data to be
placed on the bus for the required tSD. If OE is HIGH during an R/W controlled write cycle, this requirement does not apply and the write pulse can be as short as
the specified tPWE.
32. To access RAM, CE = VIL, SEM = VIH.
33. To access upper byte, CE = VIL, UB = VIL, SEM = VIH.
To access lower byte, CE = VIL, LB = VIL, SEM = VIH.
34. Transition is measured ±500 mV from steady state with a 5 pF load (including scope and jig). This parameter is sampled and not 100% tested.
35. During this period, the I/O pins are in the output state, and input signals must not be applied.
36. If the CE or SEM LOW transition occurs simultaneously with or after the R/W LOW transition, the outputs remain in the high impedance state.
Switching Waveforms (continued)
tAW
tWC
tPWE
tHD
tSD
tHA
CE
R/W
OE
DATA OUT
DATA IN
ADDRESS
tHZOE
tSA
tHZWE
tLZWE
Figure 7. Write Cycle No. 1: R/W Controlled Timing[28, 29, 30, 31]
[34]
[34]
[31]
[32,33]
NOTE 35
NOTE 35
tAW
tWC
tSCE
tHD
tSD
tHA
CE
R/W
DATA IN
ADDRESS
tSA
Figure 8. Write Cycle No. 2: CE Controlled Timing[28, 29, 30, 36]
[32,33]
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