X28HC64
SOFTWARE DATA PROTECTION
Figure 6. Timing Sequence—Byte or Page Write
V
(V
)
CC
CC
0V
AA
1555
55
0AAA
A0
1555
WRITES
OK
WRITE
PROTECTED
DATA
ADDR
t
WC
CE
≤t
BYTE
OR
PAGE
BLC MAX
WE
3857 FHD F16
Figure 7. Write Sequence for
Software Data Protection
Regardless of whether the device has previously been
protected or not, once the software data protection
algorithm is used, the X28HC64 will automatically dis-
able further writes unless another command is issued to
deactivate it. If no further commands are issued the
X28HC64 will be write protected during power-down
and after any subsequent power-up.
WRITE DATA AA
TO ADDRESS
1555
WRITE DATA 55
TO ADDRESS
0AAA
Note: Onceinitiated,thesequenceofwriteoperations
should not be interrupted.
WRITE DATA A0
TO ADDRESS
1555
BYTE/PAGE
LOAD ENABLED
WRITE DATA XX
TO ANY
ADDRESS
OPTIONAL BYTE
OR PAGE WRITE
ALLOWED
WRITE LAST
BYTE TO
LAST ADDRESS
AFTER t
RE-ENTERS DATA
WC
PROTECTED STATE
3857 FHD F17
7
XICOR [ XICOR INC. ]
