AT45DB021E datasheet(27/74 Pages) DIALOG

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AT45DB021E

DS-AT45DB021E—8789J—03/2021

Security Features

9.1

Sector Lockdown

The device incorporates a sector lockdown mechanism that allows each individual sector to be permanently locked

so that it becomes read-only (ROM). This is useful for applications that require the ability to permanently protect a

number of sectors against malicious attempts at altering program code or security information.

Warning:

Once a sector is locked down, it can never be erased or programmed, and it can never be unlocked.

To issue the sector lockdown command, a four-byte command sequence of 3Dh, 2Ah, 7Fh, and 30h must be

clocked into the device followed by three address bytes specifying any address within the sector to be locked

down. After the last address bit has been clocked in, the CS pin must be deasserted to initiate the internally self-

timed lockdown sequence. The lockdown sequence takes place in a maximum time of tP. During this time, the

RDY/BUSY bit in the Status Register indicates that the device is busy. If the device is powered-down before the

lockdown sequence is done, then the lockdown status of the sector cannot be guaranteed. In this case, it is

recommended that the user read the Sector Lockdown Register to determine the status of the appropriate sector

lockdown bits or bytes and re-issue the Sector Lockdown command if necessary.

Table 9-1.

Sector Lockdown Command

Figure 9-1. Sector Lockdown Timing

Command

Byte 1

Byte 2

Byte 3

Byte 4

Sector Lockdown

3Dh

2Ah

7Fh

30h

3Dh

2Ah

7Fh

30h

Address

byte

Address

byte

Address

byte

Each transition represents eight bits

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