AT25DF641A datasheet(29/58 Pages) DIALOG

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AT25DF641A [DATASHEET]

8793F–DFLASH–11/2017

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 or lockdown status of

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

Status Register, is used to control the hardware locking mechanism of the device. For hardware locking to be active, two

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 will be locked in the protected state, and sectors that are unprotected will be 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 will be 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 because 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 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 Register

can still be set to a Logical 1 to lock the Sector Protection Registers. This provides a software locking 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 first byte of the Status Register.

Tables 9-4 and 9-5 detail the various protection and locking states of the device.

Table 9-4.

Sector Protection Register States

Note:

1. “n” represents a sector number.

Table 9-5.

Hardware and Software Locking

Sector Protection Register

n(1)

Sector

n(1)

(Don’t Care)

Unprotected

Protected

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 will be 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 will be ignored. Global Protect and Unprotect

cannot be performed.

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