CAT28C256
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/O
7
(I/O
0
–I/O
6
are indeterminate) until the programming cycle is com-
plete. 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 CAT28C256,
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/O
6
toggling between one and zero. However, once the write
is complete, I/O
6
stops toggling and valid data can be
read from the device.
Figure 7. DATA Polling
ADDRESS
CE
WE
tOEH
OE
tWC
I/O7
DIN = X
DOUT = X
DOUT = X
28C256 F10
tOE
tOES
Figure 8. Toggle Bit
WE
CE
tOEH
OE
tOE
tOES
I/O6
(1)
tWC
(1)
28C256 F11
Note:
(1) Beginning and ending state of I/O
6
is indeterminate.
Doc. No. 25020-0A 2/98
8
CATALYST [ CATALYST SEMICONDUCTOR ]
