X88064

7

DATA PROTECTION

The X88064 provides two levels of data protection

through software control. There is a global software data

protection feature similar to the industry standard for

secondary level of data security.

SOFTWARE DATA PROTECTION

The X88064 offers a software controlled data protection

feature. The X88064 is shipped from Xicor with the soft-

ware data protection NOT ENABLED; that is, the device

will be in the standard operating mode. In this mode data

should be protected during power-up/down operations

through the use of external circuits. The host then has

stable.

The X88064 can be automatically protected during

power-up/down without the need for external circuits by

employing the software data protection feature. The inter-

nal software data protection circuit is enabled after the

first write operation utilizing the software algorithm. This

circuit is nonvolatile and will remain set for the life of the

device unless the SDP deactivation command is issued.

Once the software protection is enabled, the X88064 is

also protected from inadvertent and accidental writes in

the powered-up state. That is, the SDP software algo-

rithm must be issued prior to writing additional data to the

device.

Writing with SDP Enabled

SEQUENCE TO DEACTIVATE SOFTWARE DATA

PROTECTION

WRITE AA

TO X555

WRITE 55

TO XAAA

WRITE A0

TO X555

PERFORM BYTE

OR PAGE WRITE

OPERATIONS

EXIT ROUTINE

X = Address bit (A12) of

7023 FRM F06

the byte being updated.

WRITE AA to 555

EXIT ROUTINE

WRITE 55 to AAA

WRITE A0 to 555

WRITE AA to 555

WRITE 80 to AAA