AT45DB021E datasheet(29/74 Pages) DIALOG

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AT45DB021E

DS-AT45DB021E—8789J—03/2021

9.1.2

Freeze Sector Lockdown

The Sector Lockdown command can be permanently disabled, and the current sector lockdown state can be

permanently frozen so that 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 are ignored.

To issue the Freeze Sector Lockdown command, the CS pin must be asserted and the opcode sequence of 34h,

55h, AAh, and 40h must be clocked into the device. Any additional data clocked into the device are ignored. When

the CS pin is deasserted, the current sector lockdown state is permanently frozen within a time of tLOCK. Also, the

SLE bit in the Status Register is permanently reset to a logic 0 to indicate that the Sector Lockdown command is

permanently disabled.

Table 9-5.

Freeze Sector Lockdown

Figure 9-3. Freeze Sector Lockdown Timing

9.2

Security Register

The device contains a specialized Security Register that can be used for purposes such as unique device

serialization or locked key storage. The register is comprised of a total of 128 bytes that is divided into two portions.

The first 64 bytes (byte locations 0 through 63) of the Security Register are allocated as an One-Time

Programmable space. Once these 64 bytes have been programmed, they cannot be erased or reprogrammed.

The remaining 64 bytes of the register (byte locations 64 through 127) are factory programmed by Adesto and

contain a unique value for each device. The factory programmed data is fixed and cannot be changed.

Table 9-6.

Security Register

9.2.1

Programming the Security Register

The user programmable portion of the Security Register does not need to be erased before it is programmed.

To program the Security Register, a four-byte opcode sequence of 9Bh, 00h, 00h, and 00h must be clocked into

the device. After the last bit of the opcode sequence has been clocked into the device, the data for the contents of

the 64-byte user programmable portion of the Security Register must be clocked in.

After the last data byte has been clocked in, the CS pin must be deasserted to initiate the internally self-timed

program cycle. Programming the Security Register takes place in a time of tP, during which time the RDY/BUSY bit

Command

Byte 1

Byte 2

Byte 3

Byte 4

Freeze Sector Lockdown

34h

55h

AAh

40h

34h

55h

AAh

40h

Each transition represents eight bits

Security Register Byte Number

· · ·

127

Data Type

One-Time User Programmable

Factory Programmed by Adesto

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