we128k8-300cqa White Electronic Designs Corporation, we128k8-300cqa Datasheet - Page 11

• Manufacturer Part Number: we128k8-300cqa
• Description: 512kx8 Cmos Eeprom, We512k8-xcx, 5962-93091
• Manufacturer: White Electronic Designs Corporation

White Electronic Designs Corp. reserves the right to change products or specifi cations without notice.
May 2000
Rev. 1
NOTES:
1. Data Format: I/O
2. Write Protect state will be activated at end of write even if no other data is
3. Write Protect state will be deactivated at end of write period even if no other
4. 1 to 128 bytes of data at each of 4 blocks may be loaded in the 512Kx8.
Address Format: A
A
A
A
loaded.
data is loaded.
1 to 64 bytes of data at each of 8 blocks may be loaded in the 256Kx8 and
1 to 64 bytes on 4 blocks in the 128Kx8.
17
15
15
PROTECTION DISABLE ALGORITHM
, A
and A
and A
16
, and A
18
16
control selection of one of four blocks in the 512Kx8.
control one of the four blocks in the 128Kx8.
SOFTWARE BLOCK DATA
17
control selection of one of 8 pages in the 256Kx8.
White Electronic Designs
7-0
14
(Hex);
-A
ANY ADDRESS(4)
LOAD LAST BYTE
ADDRESS 2AAA
ADDRESS 2AAA
LAST ADDRESS
ADDRESS 5555
ADDRESS 5555
ADDRESS 5555
ADDRESS 5555
0
LOAD DATA XX
LOAD DATA AA
LOAD DATA 55
LOAD DATA 80
LOAD DATA AA
LOAD DATA 55
LOAD DATA 20
(Hex).
FIGURE 11 –
TO
TO
TO
TO
TO
TO
TO
TO
(1)
EXIT DATA
PROTECT STATE
(3)
11
SOFTWARE DATA PROTECTION
A software write protection feature may be enabled
or disabled by the user. When shipped by White
Microelectronics, the devices have 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 t
a six byte write sequence of specifi c data to specifi c
locations. Power transitions will not reset the software
write protection.
Each 32K byte block (128K bytes for the WE512K8)
of 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. The block
selection is controlled by the upper most address lines
(A
WE256K8, or A
HARDWARE DATA PROTECTION
Several methods of hardware data protection have been
implemented in the White Microelectronics EEPROM.
These are included to improve reliability during normal
operations.
a)
b)
c)
d)
17
WC
V
As V
5mSec typical before allowing write cycles.
V
While below 3.8V typical write cycles are inhibited.
Write inhibiting
Holding OE# low and either CS# or WE# high
inhibits write cycles.
Noise fi lter
Pulses of <8ns (typ) on WE# or CS# will not initiate
a write cycle.
through A
. The write protection feature can be disabled by
CC
CC
White Electronic Designs Corporation • [phone] • www.wedc.com
power on delay
sense
CC
climbs past 3.8V typical the device will wait
18
15
for the WE512K8, A
and A
WE512K8, WE256K8,
16
for the WE128K8).
WE128K8-XCX
15
through A
17
for the