Rainbow Electronics AT45DQ321 - Manual (Page 22)

22 AT45DQ321 [ADVANCE DATASHEET]
DS-45DQ321-031–DFLASH–12/2012
7.1.2 Disable Sector Protection
To disable the sector protection, a 4-byte command sequence of 3Dh, 2Ah, 7Fh, and 9Ah must be clocked into the
device. After the last bit of the opcode sequence has been clocked in, the CS pin must be deasserted to disable the
sector protection.
Table 7-2. Disable Sector Protection Command
Figure 7-2. Disable Sector Protection
7.2 Hardware Controlled Protection
Sectors specified for protection in the Sector Protection Register and the Sector Protection Register 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 programmed 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
permanently connected to GND, then the contents of the Sector Protection Register cannot be changed. If the WP pin is
deasserted or permanently connected to V
CC
, then the contents of the Sector Protection Register can be modified.
The WP pin will override the software controlled protection method but only for protecting the sectors.
Example: If the sectors were not previously protected by the Enable Sector Protection 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 Sector 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 deasserting 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 sector
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.
Figures 7-3 and Table 7-3 detail the sector protection status for various scenarios of the WP pin, the Enable Sector
Protection command, and the Disable Sector Protection command.
Command Byte 1 Byte 2 Byte 3 Byte 4
Disable Sector Protection 3Dh 2Ah 7Fh 9Ah
3Dh 2Ah 7Fh 9Ah
CS
Each transition represents eight bits
SI