X28C64
Software Data Protection
Figure 6. Timing Sequence—Byte or Page Write
VCC
0V
DATA
ADDRESS
CE
≤t
BLC MAX
WE
AA
1555
55
0AAA
A0
1555
tWPH2
tWC
WRITE
PROTECTED
(VCC)
WRITES
OK
BYTE
OR
PAGE
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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 and data has been written, the X28C64
will automatically disable further writes unless another
command is issued to cancel it. If no further commands
are issued the X28C64 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:
Once initiated, the sequence of write operations
should not be interrupted.
WRITE DATA A0
TO ADDRESS
1555
BYTE/PAGE
LOAD ENABLED
WRITE DATA XX
TO ANY
ADDRESS
WRITE LAST
BYTE TO
LAST ADDRESS
AFTER tWC
RE-ENTERS DATA
PROTECTED STATE
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7
XICOR [ XICOR INC. ]
