X28C64
Resetting Software Data Protection
Figure 8. Reset Software Data Protection Timing Sequence
V
CC
STANDARD
OPERATING
MODE
DATA
AA
55
0AAA
80
1555
AA
1555
55
0AAA
20
1555
≥t
WC
ADDRESS 1555
CE
WE
3853 FHD F18.1
Figure 9. Software Sequence to Deactivate
Software Data Protection
In the event the user wants to deactivate the software
data protection feature for testing or reprogramming in
an E2PROM programmer, the following six step algo-
WRITE DATAAA
TO ADDRESS
1555
rithm will reset the internal protection circuit. After tWC
,
the X28C64 will be in standard operating mode.
Note: Once initiated, the sequence of write opera-
tions should not be interrupted.
WRITE DATA 55
TO ADDRESS
0AAA
WRITE DATA 80
TO ADDRESS
1555
WRITE DATAAA
TO ADDRESS
1555
WRITE DATA 55
TO ADDRESS
0AAA
WRITE DATA 20
TO ADDRESS
1555
3853 ILL F19.2
8
XICOR [ XICOR INC. ]
