WE128K32-XXX
FIGURE 10 –
SOFTWARE DATA PROTECTION
SOFTWARE BLOCK DATA PROTECTION DISABLE
ALGORITHM(1)
A software write protection feature may be enabled or disabled
by the user. When shipped by White Microelectronics, the
WE-128K32-XXX has the feature disabled. Write access to the
device is unrestricted.
To enable software write protection, the user writes three access
code bytes to three special internal locations. Once write protection
has been enabled, each write to the EEPROM must use the same
three byte write sequence to permit writing. After setting software
data protection, any attempt to write to the device without the
three-byte command sequence will start the internal write timers.
No data will be written to the device, however, for the duration of
tWC. The write protection feature can be disabled by a six byte write
sequence of specific data to specific locations. Power transitions
will not reset the software write protection.
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
Each 128K byte block of the EEPROM has independent write
protection. One or more blocks may be enabled and the rest
disabled in any combination. The software write protection guards
against inadvertent writes during power transitions, or unauthorized
modification using a PROM programmer.
LOAD DATA 80
TO
ADDRESS 5555
LOAD DATA AA
TO
ADDRESS 5555
HARDWARE DATA PROTECTION
These features protect against inadvertent writes to the
WE128K32-XXX. These are included to improve reliability during
normal operation:
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA 20
TO
ADDRESS 5555
a)
VCC power on delay
As VCC climbs past 3.8V typical the device will wait 5msec
typical before allowing write cycles.
EXIT DATA
PROTECT STATE(3)
LOAD DATA XX
TO
b) VCC sense
While below 3.8V typical write cycles are inhibited.
ANY ADDRESS(4)
c) Write inhibiting
LOAD LAST BYTE
TO
LAST ADDRESS
Holding OE# low and either CS# or WE# high inhibits write
cycles.
d) Noise filter
Pulses of <8ns (typ) on WE# or CS# will not initiate a write
cycle.
NOTES:
1. Data Format: D7 - D0 (Hex);
Address Format: A16 - A0 (Hex).
2. Write Protect state will be activated at end of write even if
no other data is loaded.
3. Write Protect state will be deactivated at end of write
period even if no other data is loaded.
4. 1 to 128 bytes of data may be loaded.
10
4315.19E-0718-ss-WE128K32-XXX
Mercury Corp. - Memory and Storage Solutions • (602) 437-1520 • www.mrcy.com
MERCURY [ MERCURY UNITED ELECTRONICS INC ]
