AT45DB642D datasheet(14/55 Pages) ATMEL

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3542F–DFLASH–09/06

AT45DB642D

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.

Hardware Controlled Protection

Sectors specified for protection in the Sector Protection Register can be protected from program

and erase operations by asserting the WP pin and keeping the pin in its asserted state. Any sec-

tor specified for protection cannot be erased or reprogrammed as long as the WP pin is

asserted.

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

Table 9-1.

WP Pin and Protection Status

Time

Period

WP Pin

Enable Sector Protection Command

Disable Sector Protection

Command

Sector Protection

Status

1High

Command Not Issued Previously

–

Issue Command

–

Disabled

Enabled

Low

Enabled

3High

Command Issued During Period 1 or 2

–

Issue Command

Not Issued Yet

Issue Command

–

Enabled

Disabled

Enabled

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