AT45DB641E Datasheet, PDF (19/72 Pages) List of Unclassifed Manufacturers – 64-Mbit DataFlash (with Extra 2-Mbits), 1.7V Minimum SPI Serial Flash Memory

Figure 7-2. Disable Sector Protection
CS
SI
3Dh
2Ah
7Fh
9Ah
Each transition represents eight bits
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.
Figure 7-3. WP Pin and Protection Status
1
WP
2
3
Table 7-3. WP Pin and Protection Status
Time
Period WP Pin
1
High
2
Low
3
High
Enable Sector Protection Command
Command Not Issued Previously
—
Issue Command
X
Command Issued During Period 1 or 2
—
Issue Command
Disable Sector
Protection Command
X
Issue Command
—
X
Not Issued Yet
Issue Command
—
Sector
Protection
Status
Disabled
Disabled
Enabled
Enabled
Enabled
Disabled
Enabled
Sector
Protection
Register
Read/Write
Read/Write
Read/Write
Read
Read/Write
Read/Write
Read/Write
AT45DB641E 19
DS-45DB641E-027E–DFLASH–1/2014