28C256 datasheet(7/24 Pages) XICOR

7 / 24 page

X28C256

SOFTWARE DATA PROTECTION

Figure 6. Timing Sequence—Byte or Page Write

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Figure 7. Write Sequence for

Software Data Protection

WRITE LAST

BYTE TO

LAST ADDRESS

WRITE DATA 55

TO ADDRESS

2AAA

WRITE DATA A0

TO ADDRESS

5555

WRITE DATA XX

TO ANY

ADDRESS

AFTER tWC

RE-ENTERS DATA

PROTECTED STATE

WRITE DATA AA

TO ADDRESS

5555

BYTE/PAGE

LOAD ENABLED

3855 FHD F17

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 X28C256

will automatically disable further writes unless another

command is issued to cancel it. If no further commands

are issued the X28C256 will be write protected during

power-down and after any subsequent power-up.

Note: Once initiated, the sequence of write operations

should not be interrupted.

(VCC)

WRITE

PROTECTED

VCC

DATA

ADDR.

5555

2AAA

5555

≤t

BLC MAX

WRITES

BYTE

PAGE

tWC

≤t

BLC MAX

tWPH2

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