WME128K8-XXX
FIGURE 9 –
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
WME128K8-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
LOAD DATA AA
TO
ADDRESS 5555
LOAD DATA 55
TO
ADDRESS 2AAA
t
WC. The write protection feature can be disabled by a six byte write
LOAD DATA 80
TO
ADDRESS 5555
sequence of specific data to specific locations. Power transitions
will not reset the software write protection.
LOAD DATA AA
TO
ADDRESS 5555
The software write protection guards against inadvertent writes
during power transitions or unauthorized modification using a
PROM programmer.
LOAD DATA 55
TO
ADDRESS 2AAA
HARDWARE DATA PROTECTION
These features protect against inadvertent writes to the
WME128K8-XXX. These are included to improve reliability during
normal operation:
LOAD DATA 20
TO
ADDRESS 5555
EXIT DATA
PROTECT STATE(3)
LOAD DATA XX
a)
VCC power on delay
TO
As VCC climbs past 3.8V typical the device will wait 5msec
typical before allowing write cycles.
ANY ADDRESS(4)
LOAD LAST BYTE
TO
LAST ADDRESS
b)
V
CC sense
While below 3.8V typical write cycles are inhibited.
c) Write inhibiting
Holding OE# low and either CS# or WE# high inhibits write
cycles.
NOTES:
1. Data Format: I/O7 - I/O0 (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.
d) Noise filter
Pulses of <15ns (typ) on WE# or CS# will not initiate a write
cycle.
4. 1 to 128 bytes of data may be loaded.
9
4311.11E-0718-ss-WME128K8-XXX
Mercury Corp. - Memory and Storage Solutions • (602) 437-1520 • www.mrcy.com
MERCURY [ MERCURY UNITED ELECTRONICS INC ]
