AT25128B/AT25256B
Device Commands and Addressing
6.4.2
Write-Protect Enable Function
The WRSRinstruction also allows the user to enable or disable the Write-Protect (WP) pin through the use
of the Write-Protect Enable (WPEN) bit. When the WPEN bit is set to logic ‘0’, the ability to write the
EEPROM array is dictated by the values of the Block Write-Protect (BP<1:0>) bits. The ability to write the
STATUS register is controlled by the WEL bit. When the WPEN bit is set to logic ‘1’, the STATUS register
is read-only.
Hardware Write Protection is enabled when both the WP pin is low and the WPEN bit has been set to a
logic ‘1’. When the device is Hardware Write‑Protected, writes to the STATUS register, including the Block
Write‑Protect , WEL and WPEN bits, and to the sections in the memory array selected by the Block
Write‑Protect bits are disabled. When Hardware Write Protection is enabled, writes are only allowed to
sections of the memory that are not block‑protected.
Hardware Write Protection is disabled when either the WP pin is high or the WPEN bit is a logic ‘0’. When
Hardware Write Protection is disabled, writes are only allowed to sections of the memory that are not
block‑protected. Refer to Table 6-5 for additional information.
Note:ꢀ When the WPEN bit is Hardware Write‑Protected, it cannot be set back to a logic ‘0’ as long as
the WP pin is held low.
Table 6-5.ꢀWPEN Operation
WPEN
WP
Pin
WEL
Protected Blocks
Unprotected Blocks
STATUS Register
0
0
1
1
x
x
x
0
1
0
1
0
1
Protected
Protected
Protected
Protected
Protected
Protected
Protected
Writable
Protected
Writable
Protected
Writable
Protected
Writable
x
Low
Low
High
High
Protected
Protected
Protected
Writable
DS20006193A-page 22
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