CAT28C64B
DATA Polling
Toggle Bit
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 com-
plete. Upon completion of the self-timed write cycle, all
I/O’s will output true data during a read cycle.
In addition to the DATA Polling feature, 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
t
OEH
t
OES
t
OE
OE
t
WC
= X
I/O
D
= X
D
D
= X
OUT
7
IN
OUT
Figure 8. Toggle Bit
WE
CE
OE
t
OEH
t
OES
t
OE
(1)
(1)
I/O
6
t
WC
Note:
(1) Beginning and ending state of I/O is indeterminate.
6
Doc. No. 1011, Rev. F
9
CATALYST [ CATALYST SEMICONDUCTOR ]
