AT25DF641_13 datasheet(30/56 Pages) ETC2

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AT25DF641

3680F–DFLASH–4/10

9.2.

Freeze Sector Lockdown State

The current sector lockdown state can be permanently frozen so that no f urther modifications to the Sector

Lockdown Registers can be made; therefore, the Sector Lockdown command will be permanently disabled, and

no additional sectors can be locked down aside from those already locked down. Any attempts to issue the Sector

Lockdown command after the sector lockdown state has been frozen will be ignored.

Before the Freeze Sector Lockdown State 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”. In addition, the Sector Lockdown

Enabled (SLE) bit in the Status Register must have also been previously set to the logical “1” state. To issue the

Freeze Sector Lockdown State command, the

pin must first be asserted and the opcode of 34h must be

clocked into the device followed by three command specific address bytes of 55AA40h. After the three address

bytes have been c locked in, a c onfirmation byte of D0h must be c locked in immediately following the three

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

pin is deasserted, the

current sector lockdown state will be permanently frozen within a time of tLOCK. In addition, the WEL bit in the

Status Register will be reset back to the logical “0” state, and the SLE bit will be permanently reset to a logical “0”

to indicate that the Sector Lockdown command is permanently disabled.

The complete and correct three address bytes and the confirmation byte 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 Freeze Sector Lockdown State

operation, the WEL bit in the Status Register will be reset to a logical “0”; however, the state of the SLE bit will be

unchanged.

Figure 9-2.

Freeze Sector Lockdown State

SCK

MS B

37 38

31 32

29 30

OP C ODE

HIG H-IMP E DANC E

MS B

ADDR E S S B ITS A23-A0 C ONF IR MATION B Y TE IN

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