AT25DF081A datasheet(19/54 Pages) ETC2

19 / 54 page

8715C–SFLSH–1/2013

AT25DF081A

9.3

Protect Sector

Every physical 64-Kbyte sector of the device has a corresponding single-bit Sector Protection Register that is used

to control the software protection of a sector. Upon device power-up, each Sector Protection Register will default to

the logical “1” state indicating that all sectors are protected and cannot be programmed or erased.

Issuing the Protect Sector command to a particular sector address will set the corresponding Sector Protection

Before the Protect Sector command can be issued, the Write Enable command must have been previously issued

to set the WEL bit in the Status Register to a logical “1”. To issue the Protect Sector command, the CS pin must

first be asserted and the opcode of 36h must be clocked into the device followed by three address bytes designat-

ing any address within the sector to be protected. Any additional data clocked into the device will be ignored. When

the CS pin is deasserted, the Sector Protection Register corresponding to the physical sector addressed by A23-

A0 will be set to the logical “1” state, and the sector itself will then be protected from program and erase operations.

In addition, the WEL bit in the Status Register will be reset back to the logical “0” state.

The complete three address bytes must be clocked into the device before the CS pin is deasserted, and the CS pin

must be deasserted on an even byte boundary (multiples of eight bits); otherwise, the device will abort the opera-

tion. When the device aborts the Protect Sector operation, the state of the Sector Protection Register will be

unchanged, and the WEL bit in the Status Register will be reset to a logical “0”.

As a safeguard against accidental or erroneous protecting or unprotecting of sectors, the Sector Protection Regis-

ters can themselves be locked from updates by using the SPRL (Sector Protection Registers Locked) bit of the

Status Register (please refer to the Status Register description for more details). If the Sector Protection Registers

are locked, then any attempts to issue the Protect Sector command will be ignored, and the device will reset the

WEL bit in the Status Register back to a logical “0” and return to the idle state once the CS pin has been

deasserted.

Figure 9-3.

Protect Sector

Table 9-1.

Sector Protection Register Values

Value

Sector Protection Status

Sector is unprotected and can be programmed and erased.

Sector is protected and cannot be programmed or erased. This is the default state.

SCK

MSB

00110110

410 11

812

29 30

27 28

OPCODE

AAAA

AAA

ADDRESS BITS A23-A0

HIGH-IMPEDANCE

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