X28VC256
RESETTING SOFTWARE DATA PROTECTION
Figure 8. Reset Software Data Protection Timing Sequence
VCC
DATA
ADDRESS
CE
AA
5555
55
2AAA
80
5555
AA
5555
55
2AAA
20
5555
tWC
STANDARD
OPERATING
MODE
WE
3869 FHD F18
Figure 9. Write Sequence for Resetting
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 X28VC256 will be in standard operating mode.
WRITE DATA AA
TO ADDRESS
5555
WRITE DATA 55
TO ADDRESS
2AAA
Note:
Once initiated, the sequence of write operations
should not be interrupted.
WRITE DATA 80
TO ADDRESS
5555
WRITE DATA AA
TO ADDRESS
5555
WRITE DATA 55
TO ADDRESS
2AAA
WRITE DATA 20
TO ADDRESS
5555
AFTER tWC,
RE-ENTERS
UNPROTECTED
STATE
3869 FHD F19
8
XICOR [ XICOR INC. ]
