WE256K8-150CC Просмотр технического описания (PDF) - White Electronic Designs => Micro Semi
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WE256K8-150CC Datasheet PDF : 13 Pages
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White Electronic Designs
WE512K8, WE256K8,
WE128K8-XCX
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/O7
complemented during the programming cycle, and I/O7
true after completion.
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/O7. For example,
if the data written consisted of I/O7 = HIGH, then the data
read back would consist of I/O7 = LOW.
A polled byte write sequence would consist of the following
steps:
1. write byte to EEPROM
2. store last byte and last address written
3. release a time slice to other tasks
4. read byte from EEPROM - last address
5. compare I/O7 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
VCC = 5.0V, VSS = 0V, -55°C ≤ TA ≤ +125°C
Parameter
Symbol
512Kx8
256Kx8
128Kx8
Unit
Min
Max
Min
Max
Min
Max
Data Hold Time
tDH
10
0
0
ns
Output Enable Hold Time
tOEH
10
0
0
ns
Output Enable To Output Delay
tOE
100
100
100
ns
Write Recovery Time
tWR
0
0
0
ns
FIGURE 8 – DATA POLLING WAVEFORMS
WE1-4#
CS1-4#
OE#
I/O7
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
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