11

AT45DB321D [DATASHEET]

3597T–DFLASH–11/2013

6.1.2

Disable Sector Protection Command

To disable sector protection using the software controlled method, the CS pin must first be asserted, as it would be with any

other command. Once the CS pin has been asserted, the appropriate four-byte sequence for the disable sector protection

command must be clocked in via the input pin (SI). After the last bit of the command sequence has been clocked in, the CS pin

must be deasserted, after which the sector protection will be disabled. The WP pin must be in the deasserted state; otherwise,

the disable sector protection command will be ignored.

Table 6-2.

Disenable Sector Protection Command

Command

Byte 1

Byte 2

Byte 3

Byte 4

Figure 6-2. Disable Sector Protection

6.1.3

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 protection is desired and if the WP pin is not used.

7.

Hardware Controlled Protection

Sectors specified in the sector protection register for protection, 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 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 permanently connected to GND, then the content

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 protection command, then simply asserting the WP pin would enable

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 sector protection. In this case, the disable sector protection command

would need to be issued while the WP pin is deasserted to disable 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.

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 7-1. WP Pin and Protection Status

Disable sector protection

3DH

2AH

7FH

9AH

Opcode

Byte 1

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

CS

Each transition

represents 8 bits

SI

WP

12

3