25c040xt Microchip Technology Inc., 25c040xt Datasheet - Page 9

• Manufacturer Part Number: 25c040xt
• Description: 4k Spi Bus Serial Eeprom
• Manufacturer: Microchip Technology Inc.

3.4
The 25XX040 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:
© 2006 Microchip Technology Inc.
Write Enable (WREN) and Write
Disable (WRDI)
WRITE ENABLE SEQUENCE
WRITE DISABLE SEQUENCE
SCK
SCK
CS
CS
SO
SO
SI
SI
0
0
0
0
25AA040/25LC040/25C040
0
0
See
1
1
High-impedance
High-impedance
0
0
2
2
0
0
3
3
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
• WP line is low
0
0
4
4
1
1
5
5
1
1 0
6
6
0
0
7
7
DS21204E-page 9