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White Electronic Designs Corporation Phoenix AZ (602) 437-1520
WE128K32-XXX
White Electronic Designs
HARDWARE DATA PROTECTION
These features protect against inadvertent writes to
the WE128K32-XXX. These are included to
improve reliability during normal operation:
a) VCC power on delay
As VCC climbs past 3.8V typical the device will
wait 5msec typical before allowing write cycles.
b) VCC sense
While below 3.8V typical write cycles are inhib-
ited.
c) Write inhibiting
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.
SOFTWARE DATA PROTECTION
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.
Each 128K byte block of the EEPROM has indepen-
dent 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 program-
mer.
SOFTWARE DATA PROTECTION
DISABLE ALGORITHM(1)
EXIT DATA
PROTECT STATE
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.
(3)
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA 80
TO
ADDRESS 5555
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
LOAD DATA 20
TO
ADDRESS 5555
LOAD DATA XX
TO
ANY ADDRESS(4)
LOAD LAST BYTE
TO
LAST ADDRESS
FIG. 11