20 Megabit (512K x 40-Bit) EEPROM MCM
2. Data Protection at V
CC
on/off
79LV2040
When V
CC
is turned on or off, noise on the control pins generated by external circuits, such as CPUs, may turn the EEPROM to
programming mode by mistake. To prevent this unintentional programming, the EEPROM must be kept in unprogrammable
state during V
CC
on/off by using a CPU reset signal to RES pin.
3. RES Signal
RES should be kept at V
SS
level when V
CC
is turned on or off. The EEPROM breaks off programming operation when RES
become low, programming operation doesn’t finish correctly in case that RES falls low during programming operation. RES
should be kept high for 10 ms after the last data is input
.
Memory
15ms
4. Software Data Protection Enable
The 79LV2040contains a software controlled write protection feature that allows the user to inhibit all write operations to the
device. This is useful in protecting the device from unwanted write cycles due to uncontrollable circuit noise or inadvertent
writes caused by minor bus contentions. Software data protection is enabled by writing the following data sequence to the
EEPROM and allowing the write cycle period (t
WC
) of 15ms to elapse:
.
Software Data Protection Enable Sequence
Address
5555
AAAA or 2AAA
5555
Data
AA AA AA AA AA
55 55 55 55 55
A0 A0 A0 A0 A0
09.07.05 Rev 1
All data sheets are subject to change without notice
13
©2005 Maxwell Technologies
All rights reserved
MAXWELL [ MAXWELL TECHNOLOGIES ]
