AT25PE20 datasheet(17/64 Pages) DIALOG

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AT25PE20

DS-25PE20–139C–8/2018

Sector Protection

Two protection methods, hardware and software controlled, are provided for protection against inadvertent or erroneous

program and erase cycles. The software controlled method relies on the use of software commands to enable and

disable sector protection while the hardware controlled method employs the use of the Write Protect (WP) pin. The

selection of which sectors that are to be protected or unprotected against program and erase operations is specified in

the nonvolatile Sector Protection Register. The status of whether or not sector protection has been enabled or disabled

by either the software or the hardware controlled methods can be determined by checking the Status Register.

7.1

Software Sector 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.

7.1.1

Enable Sector Protection

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, a 4-byte command sequence of

3Dh, 2Ah, 7Fh, and A9h must be clocked into the device. After the last bit of the opcode sequence has been clocked in,

the CS pin must be deasserted to enable the Sector Protection.

Table 7-1.

Enable Sector Protection Command

Figure 7-1.

Enable Sector Protection

7.1.2

Disable Sector Protection

To disable the sector protection, a 4-byte command sequence of 3Dh, 2Ah, 7Fh, and 9Ah must be clocked into the

device. After the last bit of the opcode sequence has been clocked in, the CS pin must be deasserted to disable the

sector protection.

Table 7-2.

Disable Sector Protection Command

Figure 7-2.

Disable Sector Protection

Command

Byte 1

Byte 2

Byte 3

Byte 4

Enable Sector Protection

3Dh

2Ah

7Fh

A9h

3Dh

2Ah

7Fh

9Ah

Each transition represents eight bits

A9h

Command

Byte 1

Byte 2

Byte 3

Byte 4

Disable Sector Protection

3Dh

2Ah

7Fh

9Ah

3Dh

2Ah

7Fh

9Ah

Each transition represents eight bits

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