Rainbow Electronics AT45DB321D - Manual (Page 13)

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3597J–DFLASH–4/08
AT45DB321D
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 below 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
WP
1 2 3
Table 9-1. WP Pin and Protection Status
Time
Period WP Pin
Enable Sector Protection
Command
Disable Sector
Protection Command
Sector Protection
Status
Sector
Protection
Register
1 High
Command Not Issued Previously
–
Issue Command
X
Issue Command
–
Disabled
Disabled
Enabled
Read/Write
Read/Write
Read/Write
2 Low X X Enabled Read Only
3 High
Command Issued During Period 1
or 2
–
Issue Command
Not Issued Yet
Issue Command
–
Enabled
Disabled
Enabled
Read/Write
Read/Write
Read/Write