25AA640 MICROCHIP [Microchip Technology], 25AA640 Datasheet - Page 8

• Manufacturer Part Number: 25AA640
• Description: 64K SPI Bus Serial EEPROM
• Manufacturer: MICROCHIP [Microchip Technology]

25AA640/25LC640/25C640
3.4
The 25xx640 contains a write enable latch.
Table 3-3 for the Write Protect Functionality Matrix.
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:
FIGURE 3-5:
DS21223A-page 8
Write Enable (WREN) and Write
Disable (WRDI)
WRITE ENABLE SEQUENCE
WRITE DISABLE SEQUENCE
SCK
SCK
CS
SO
CS
SO
SI
SI
0
0
0
0
0
0
See
1
1
Preliminary
high impedance
high impedance
0
0
2
2
0
0
3
3
0
0
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
4
4
1
1
5
5
1
1 0
6
6
0
0
7
7
1997 Microchip Technology Inc.