AT25DF321A datasheet(26/51 Pages) RENESAS

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3686I–DFLASH–02/2019

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 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); 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

37 38

31 32

29 30

OPCODE

HIGH-IMPEDANCE

MSB

ADDRESS BITS A23-A0

CONFIRMATION BYTE IN

SCK

MSB

37 38

31 32

29 30

OPCODE

HIGH-IMPEDANCE

MSB

ADDRESS BITS A23-A0

CONFIRMATION BYTE IN

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