X28C256
RESETTING SOFTWARE DATA PROTECTION
Figure 8. Reset Software Data Protection Timing Sequence
V
CC
STANDARD
OPERATING
MODE
DATA AA
ADDR. 5555
55
2AAA
80
5555
AA
5555
55
2AAA
20
5555
≥t
WC
CE
WE
3855 FHD F18
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
2
WRITE DATA AA
TO ADDRESS
5555
an E PROM programmer, the following six step algo-
rithm will reset the internal protection circuit. After t
the X28C256 will be in standard operating mode.
,
WC
Note: Onceinitiated,thesequenceofwriteoperations
should not be interrupted.
WRITE DATA 55
TO ADDRESS
2AAA
WRITE DATA 80
TO ADDRESS
5555
WRITE DATA AA
TO ADDRESS
5555
WRITE DATA 55
TO ADDRESS
2AAA
WRITE DATA 20
TO ADDRESS
5555
3855 FHD F19
8
XICOR [ XICOR INC. ]
