X28HC64
RESETTING SOFTWARE DATA PROTECTION
Figure 8. Reset Software Data Protection Timing Sequence
Vcc
STANDARD
OPERATING
MODE
DATA AA
ADDR 1555
55
0AAA
80
1555
AA
1555
55
0AAA
20
1555
≥t
WC
CE
WE
3857 ILL F18.2
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 DATA AA
TO ADDRESS
1555
rithm will reset the internal protection circuit. After tWC
,
the X28HC64 will be in standard operating mode.
Note: Onceinitiated,thesequenceofwriteoperations
should not be interrupted.
WRITE DATA 55
TO ADDRESS
0AAA
WRITE DATA 80
TO ADDRESS
1555
WRITE DATA AA
TO ADDRESS
1555
WRITE DATA 55
TO ADDRESS
0AAA
WRITE DATA 20
TO ADDRESS
1555
3857 ILL F19.2
8
XICOR [ XICOR INC. ]
