Rainbow Electronics AT45DB011D - Manual (Page 12)

12
3639J–DFLASH–11/2012
AT45DB011D
Figure 8-2. Disable Sector Protection
8.1.3 Various Aspects About Software Controlled Protection
Software controlled protection is useful in applications in which the WP pin is not or cannot be
controlled by a host processor. In such instances, the WP pin may be left floating (the WP pin is
internally pulled high) and sector protection can be controlled using the Enable Sector Protection
and Disable Sector Protection commands.
If the device is power cycled, then the software controlled protection will be disabled. Once the
device is powered up, the Enable Sector Protection command should be reissued if sector pro-
tection is desired and if the WP pin is not used.
9. Hardware Controlled Protection
Sectors specified for protection in the Sector Protection Register and the Sector Protection Reg-
ister itself can be protected from program and erase operations by asserting the WP pin and
keeping the pin in its asserted state. The Sector Protection Register and any sector specified for
protection cannot be erased or reprogrammed as long as the WP pin is asserted. In order to
modify the Sector Protection Register, the WP pin must be deasserted. If the WP pin is perma-
nently connected to GND, then the content of the Sector Protection Register cannot be changed.
If the WP pin is deasserted, or permanently connected to V
CC
, then the content of the Sector
Protection Register can be modified.
The WP pin will override the software controlled protection method but only for protecting the
sectors. For example, if the sectors were not previously protected by the Enable Sector Protec-
tion command, then simply asserting the WP pin would enable the sector protection within the
maximum specified t
WPE
time. When the WP pin is deasserted; however, the sector protection
would no longer be enabled (after the maximum specified t
WPD
time) as long as the Enable Sec-
tor Protection command was not issued while the WP pin was asserted. If the Enable Sector
Protection command was issued before or while the WP pin was asserted, then simply deassert-
ing the WP pin would not disable the sector protection. In this case, the Disable Sector
Protection command would need to be issued while the WP pin is deasserted to disable the sec-
tor protection. The Disable Sector Protection command is also ignored whenever the WP pin is
asserted.
A noise filter is incorporated to help protect against spurious noise that may inadvertently assert
or deassert the WP pin.
The Table 9-1 details the sector protection status for various scenarios of the WP pin, the
Enable Sector Protection command, and the Disable Sector Protection command.
Figure 9-1. WP Pin and Protection Status
Opcode
Byte 1
Opcode
Byte 2
Opcode
Byte 3
Opcode
Byte 4
CS
Each transition
represents 8 bits
SI
WP
1 2 3