AT25DF021A datasheet(28/59 Pages) RENESAS

28 / 59 page

DS-AT25DF021A-042 Rev. J

Page 28

12/22/22

AT25DF021A Datasheet

9.7

Protected States and the Write Protect (WP) Pin

The WP pin is not linked to the memory array itself and has no direct effect on the protection status of the memory

array. Instead, the WP pin, in conjunction with the SPRL (Sector Protection Registers Locked) bit in the Status

conditions must be met – the WP pin must be asserted and the SPRL bit must be in the logical 1 state.

When hardware locking is active, the Sector Protection Registers are locked and the SPRL bit itself is also locked.

Therefore, sectors that are protected are locked in the protected state, and sectors that are unprotected are

locked in the unprotected state. These states cannot be changed as long as hardware locking is active, so the

Protect Sector, Unprotect Sector, and Write Status Register commands are ignored. In order to modify the

protection status of a sector, the WP pin must first be deasserted, and the SPRL bit in the Status Register must be

reset back to the logical 0 state using the Write Status Register command. When resetting the SPRL bit back to a

logical 0, it is not possible to perform a Global Protect or Global Unprotect at the same time since the Sector

Protection Registers remain soft-locked until after the Write Status Register command has been executed.

If the WP pin is permanently connected to GND, then once the SPRL bit is set to a logical 1, the only way to reset

the bit back to the logical 0 state is to power-cycle or reset the device. This allows a system to power-up with all

sectors software protected but not hardware locked. Therefore, sectors can be unprotected and protected as

needed and then hardware locked at a later time by simply setting the SPRL bit in the Status Register.

When the WP pin is deasserted, or if the WP pin is permanently connected to VCC, the SPRL bit in the Status

ability to prevent erroneous Protect Sector or Unprotect Sector commands from being processed. When changing

the SPRL bit to a logical 1 from a logical 0, it is also possible to perform a Global Protect or Global Unprotect at the

same time by writing the appropriate values into bits 5, 4, 3, and 2 of the Status Register.

Tables 6 and 7 detail the various protection and locking states of the device.

Table 6. Sector Protection Register States

Sector Protection Register

n[1]

1. “n” represents a sector number

Sector

n(1)

(Don't Care)

Unprotected

1Protected

Table 7. Hardware and Software Locking

SPRL

Locking

SPRL Change Allowed

Sector Protection Registers

Can be modified from 0 to 1

Unlocked and modifiable using the Protect and

Unprotect Sector commands. Global Protect and

Unprotect can also be performed.

Hardware

Locked

Locked in current state. Protect and Unprotect

Sector commands are ignored. Global Protect

and Unprotect cannot be performed.

Can be modified from 0 to 1

Unlocked and modifiable using the Protect and

Unprotect Sector commands. Global Protect and

Unprotect can also be performed.

Software

Locked

Can be modified from 1 to 0

Locked in current state. Protect and Unprotect

Sector commands are ignored. Global Protect

and Unprotect cannot be performed.

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