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AT25DN011

DS-25DN011–038H–8/2021

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

Status Register command will be ignored. In order to modify the protection status of the memory array, the WP pin must

first be deasserted, and the BPL bit in the Status Register must be reset back to the logical “0” state using the Write

Status Register command.

If the WP pin is permanently connected to GND, then once the BPL 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 BPL bit in the Status Register.

be set to a logical “1”, but doing so will not lock the BP0 bit.

Table 9-2 details the various protection and locking states of the device.

10.

Security Commands

10.1 Program OTP Security Register

The device contains a specialized OTP (One-Time Programmable) Security Register that can be used for purposes such

as unique device serialization, system-level Electronic Serial Number (ESN) storage, locked key storage, etc. The OTP

Security Register is independent of the main Flash memory array and is comprised of a total of 128 bytes of memory

divided into two portions. The first 64 bytes (byte locations 0 through 63) of the OTP Security Register are allocated as a

one-time user-programmable space. Once these 64 bytes have been programmed, they cannot be erased or

reprogrammed. The remaining 64 bytes of the OTP Security Register (byte locations 64 through 127) are factory

programmed by Adesto and will contain a unique value for each device. The factory programmed data is fixed and

cannot be changed.

Table 9-2.

Hardware and Software Locking

WP

BPL

Locking

BPL Change Allowed

BP0 and Protection Status

0

0

Can be modified from 0 to 1

BP0 bit unlocked and modifiable using the Write

Status Register command. Memory array can be

protected and unprotected freely.

0

1

Hardware

Locked

Locked

BP0 bit locked in current state. The Write Status

Register command will have no affect. Memory

array is locked in current protected or unprotected

state.

1

0

Can be modified from 0 to 1

BP0 bit unlocked and modifiable using the Write

Status Register command. Memory array can be

protected and unprotected freely.

1

1

Can be modified from 1 to 0

BP0 bit unlocked and modifiable using the Write

Status Register command. Memory array can be

protected and unprotected freely.

Table 10-1. OTP Security Register

Security Register

Byte Number

0

1

. . .

62

63

64

65

. . .

126

127

One-Time User Programmable

Factory Programmed by Adesto