AT25DF321A-MH-T datasheet(26/52 Pages) ATMEL

26 / 52 page

3686D–DFLASH–12/09

Atmel AT25DF321A

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 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 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 sector lockdown state will be permanently

frozen within a time of t

LOCK. 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); 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 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

AT25DF321A-MH-T Datenblatt(PDF) 26 Page - ATMEL Corporation

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