AT25DF081A datasheet(26/54 Pages) ETC2

26 / 54 page

8715C–SFLSH–1/2013

AT25DF081A

Figure 10-1. Sector Lockdown

10.2 Freeze Sector Lockdown State

The current sector lockdown state can be permanently frozen so that no further modifications to the Sector Lock-

down 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 CS 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 clocked in, a confirmation byte of D0h must be clocked in immediately following the three address

bytes. Any additional data clocked into the device will be ignored. When the CS pin is deasserted, the current sec-

tor 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

CS pin is deasserted, and the CS pin must be deasserted on an even byte boundary (multiples of eight bits); other-

wise, 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 10-2. Freeze Sector Lockdown State

SCK

MSB

00110011

839

37 38

31 32

29 30

OPCODE

HIGH-IMPEDANCE

AAA

MSB

1101000

ADDRESS BITS A23-A0

CONFIRMATION BYTE IN

SCK

MSB

00110100

839

37 38

31 32

29 30

OPCODE

HIGH-IMPEDANCE

000

MSB

1101000

ADDRESS BITS A23-A0

CONFIRMATION BYTE IN

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