CAT28C257_04 Datasheet, PDF (8/12 Pages) Catalyst Semiconductor – 256K-Bit CMOS PARALLEL EEPROM

CAT28C257
DATA Polling
DATA polling is provided to indicate the completion of
write cycle. Once a byte write or page write cycle is
initiated, attempting to read the last byte written will
output the complement of that data on I/O₇ (I/O₀–I/O₆
are indeterminate) until the programming cycle is
complete. Upon completion of the self-timed write cycle,
all I/O’s will output true data during a read cycle.
Toggle Bit
In addition to the DATA Polling feature of the CAT28C257,
the device offers an additional method for determining
the completion of a write cycle. While a write cycle is in
progress, reading data from the device will result in I/O₆
toggling between one and zero. However, once the write
is complete, I/O₆ stops toggling and valid data can be
read from the device.
Figure 7. DATA Polling
ADDRESS
CE
WE
OE
I/O7
Figure 8. Toggle Bit
WE
tOEH
DIN = X
tOE
tWC
DOUT = X
tOES
DOUT = X
CE
tOEH
tOE
OE
tOES
I/O6
(1)
(1)
tWC
Note:
(1) Beginning and ending state of I/O₆ is indeterminate.
Doc. No. 1015, Rev. D
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