X28C64
Resetting Software Data Protection
Figure 8. Reset Software Data Protection Timing Sequence
VCC
STANDARD
OPERATING
MODE
DATA
ADDRESS
CE
AA
1555
55
0AAA
80
1555
AA
1555
55
0AAA
20
1555
≥t
WC
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 E
2
PROM programmer, the following six step algo-
rithm will reset the internal protection circuit. After t
WC
,
the X28C64 will be in standard operating mode.
WRITE DATA AA
TO ADDRESS
1555
WRITE DATA 55
TO ADDRESS
0AAA
Note:
Once initiated, the sequence of write opera-
tions should not be interrupted.
WRITE DATA 80
TO ADDRESS
1555
WRITE DATA AA
TO ADDRESS
1555
WRITE DATA 55
TO ADDRESS
0AAA
WRITE DATA 20
TO ADDRESS
1555
3853 ILL F19.2
8
XICOR [ XICOR INC. ]
