X88064 Datasheet, PDF (7/15 Pages) Xicor Inc. – E2 Micro-Peripheral

X88064
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
E²PROMs and a new Block Lock Control providing a
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
open read and write access of the device once V_CC is
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
WRITE AA
TO X555
WRITE 55
TO XAAA
WRITE A0
TO X555
PERFORM BYTE
OR PAGE WRITE
OPERATIONS
X = Address bit (A12) of
the byte being updated.
WAIT t_WC
EXIT ROUTINE
7023 FRM F06
SEQUENCE TO DEACTIVATE SOFTWARE DATA
PROTECTION
WRITE AA to 555
WRITE 55 to AAA
WRITE A0 to 555
WRITE AA to 555
WRITE 80 to AAA
WAIT OF t_wc
EXIT ROUTINE
7