AT25DF641A datasheet(25/58 Pages) DIALOG

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AT25DF641A [DATASHEET]

8793F–DFLASH–11/2017

9.4

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 9-4 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 CS pin must first be

asserted and then the opcode of 39h must be clocked 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 CS 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.

The three complete address bytes 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, 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 locking or unlocking 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

(see Section 11., “Status Register Commands” on page 35 for more details). If the Sector Protection Registers are

locked, then any attempts to issue the Unprotect 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 CS pin has been deasserted.

Figure 9-4. Unprotect Sector

SCK

MSB

00111001

410 11

812

29 30

27 28

Opcode

AAAA

AAA

Address Bits A23-A0

High-impedance

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