X28C64
Software Data Protection
Figure 6. Timing Sequence—Byte or Page Write
V
(V
)
CC
CC
0V
DATA
AA
55
0AAA
A0
1555
t
t
WC
WRITE
PROTECTED
WPH2
ADDRESS 1555
WRITES
OK
CE
≤t
BYTE
OR
PAGE
BLC MAX
WE
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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
algorithmisusedanddatahasbeenwritten,theX28C64
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: Onceinitiated,thesequenceofwriteoperations
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 t
RE-ENTERS DATA
WC
PROTECTED STATE
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3853 FHD F17
7
XICOR [ XICOR INC. ]
