White Electronic Designs
DATA POLLING
Operation with data polling permits a faster method of
writing to the EEPROM. The actual time to complete the
memory programming cycle is faster than the guaranteed
maximum.
The EEPROM features a method to determine when
the internal programming cycle is completed. After a
write cycle is initiated, the EEPROM will respond to read
cycles to provide the microprocessor with the status
of the programming cycle. The status consists of the
last data byte written being returned with data bit I/O
7
complemented during the programming cycle, and I/O
7
true after completion.
WE512K8, WE256K8,
WE128K8-XCX
Data polling allows a simple bit test operation to
determine the status of the EEPROM. During the internal
programming cycle, a read of the last byte written will
produce the complement of the data on I/O
7
. For example,
if the data written consisted of I/O
7
= HIGH, then the data
read back would consist of I/O
7
= LOW.
A polled byte write sequence would consist of the following
steps:
1.
2.
3.
4.
5.
write byte to EEPROM
store last byte and last address written
release a time slice to other tasks
read byte from EEPROM - last address
compare I/O
7
to stored value
a) If different, write cycle is not completed, go to
step 3.
b) If same, write cycle is completed, go to step 1 or
step 3.
DATA POLLING AC CHARACTERISTICS
V
CC
= 5.0V, V
SS
= 0V, -55°C ≤ T
A
≤ +125°C
Parameter
Data Hold Time
Output Enable Hold Time
Output Enable To Output Delay
Write Recovery Time
Symbol
t
DH
t
OEH
t
OE
t
WR
Min
10
10
0
512Kx8
Max
Min
0
0
0
256Kx8
Max
Min
0
0
0
128Kx8
Max
ns
ns
ns
ns
Unit
100
100
100
FIGURE 8 – DATA POLLING WAVEFORMS
WE
1-4
#
CS
1-4
#
OE#
I/O
7
ADDRESS
White Electronic Designs Corp. reserves the right to change products or specifications without notice.
May 2000
Rev. 1
8
White Electronic Designs Corporation • (602) 437-1520 • www.wedc.com
WEDC [ WHITE ELECTRONIC DESIGNS CORPORATION ]
