AT45DB021D_08 datasheet(12/52 Pages) ATMEL

12 / 52 page

3638F–DFLASH–4/08

AT45DB021D

8.1

Software Sector Protection

8.1.1

Enable Sector Protection Command

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

and erase operations by issuing the Enable Sector Protection command. To enable the 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 4-byte command

sequence 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

enabled.

Figure 8-1.

Enable Sector Protection

8.1.2

Disable Sector Protection Command

To disable the 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 4-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.

Figure 8-2.

Disable Sector Protection

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.

Command

Byte 1

Byte 2

Byte 3

Byte 4

Enable Sector Protection

3DH

2AH

7FH

A9H

Opcode

Byte 1

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

Each transition

represents 8 bits

Command

Byte 1

Byte 2

Byte 3

Byte 4

Disable Sector Protection

3DH

2AH

7FH

9AH

Opcode

Byte 1

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

Each transition

represents 8 bits

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