25AA640/25LC640
3.4
Write Enable (WREN) and
Write Disable (WRDI)
The following is a list of conditions under which the
write enable latch will be reset:
•
•
•
•
Power-up
WRDI
instruction successfully executed
WRSR
instruction successfully executed
WRITE
instruction successfully executed
The 25XX640 contains a write enable latch. See
This latch must be set before any write operation will be
completed internally. The
WREN
instruction will set the
latch, and the
WRDI
will reset the latch.
FIGURE 3-4:
WRITE ENABLE SEQUENCE
CS
0
SCK
1
2
3
4
5
6
7
SI
0
0
0
0
0
1
1
0
High-Impedance
SO
FIGURE 3-5:
WRITE DISABLE SEQUENCE
CS
0
SCK
1
2
3
4
5
6
7
SI
0
0
0
0
0
1
0
1
0
High-Impedance
SO
©
2008 Microchip Technology Inc.
DS21223H-page 9