25lc640a Microchip Technology Inc., 25lc640a Datasheet - Page 9

• Manufacturer Part Number: 25lc640a
• Description: 64k Spi Bus Serial Eeprom
• Manufacturer: Microchip Technology Inc.

2.4
The 25XX640A contains a write enable latch.
Table 2-4 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 2-4:
FIGURE 2-5:
© 2007 Microchip Technology Inc.
Write Enable (WREN) and Write
Disable (WRDI)
WRITE ENABLE SEQUENCE (WREN)
WRITE DISABLE SEQUENCE (WRDI)
SCK
CS
SO
SCK
SI
CS
SO
SI
0
0
0
0
0
1
0
1
See
High-Impedance
0
High-Impedance
0
2
2
0
0
3
3
25AA640A/25LC640A
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
0
0
4
4
1
5
1
5
1
6
0
6
0
7
0
7
DS21830C-page 9