AT25DF641_13 datasheet(23/56 Pages) ETC2

23 / 56 page

AT25DF641

3680F–DFLASH–4/10

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

pin must

first be as serted and the opcode of 36h must be clocked into the device followed by three address bytes

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

ignored. When the

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

pin is deasserted, and the

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

operation. 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

Registers 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 Commands 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

pin has been deasserted.

Figure 8-3.

Protect Sector

SCK

MS B

10 11

29 30

27 28

OP C ODE

ADDR E S S B ITS A23-A0

HIG H-IMP E DANC E

8.4.

Unprotect Sector

Issuing the Unprotect Sector command to a particular sector address will reset the corresponding Sector

Protection Register to the logical “0” state (see Table 8-2 for Sector Protection Register values). Every physical

sector of the device has a corresponding single-bit Sector Protection Register that is used to control the software

protection of a sector.

Before the Unprotect 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 Unprotect Sector command, the

pin must first be as serted and the opcode of 39h must be c locked into the device. After the opcode has been

clocked in, the three address bytes designating any address within the sector to be unprotected must be clocked

in. Any additional data clocked into the device after the address bytes will be ignored. When the

pin is

deasserted, the Sector Protection Register corresponding to the sector addressed by A23-A0 will be reset to the

logical “0” state, and the sector itself will be unprotected. In addition, the WEL bit in the Status Register will be

reset back to the logical “0” state.

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