AT45DB321E datasheet(22/69 Pages) RENESAS

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AT45DB321E

8784M–DFLASH–02/2022

Figure 6-7.

Read Sector Protection Register

6.16.4 About the Sector Protection Register

The Sector Protection Register is subject to a limit of 10,000 erase/program cycles. Users are encouraged to carefully

evaluate the number of times the Sector Protection Register will be modified during the course of the application’s life

cycle. If the application requires that the Security Protection Register be modified more than the specified limit of 10,000

cycles because the application needs to temporarily unprotect individual sectors (sector protection remains enabled

while the Sector Protection Register is reprogrammed), then the application will need to limit this practice. Instead, a

combination of temporarily unprotecting individual sectors along with disabling sector protection completely will need to

be implemented by the application to ensure that the limit of 10,000 cycles is not exceeded.

Security Features

7.1

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 4-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 should take place in a maximum time of t

P. During this time, the RDY/BUSY bit in the Status

sequence, 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 7-1.

Sector Lockdown Command

32h

Data

n + 1

Data

n + 63

Each transition represents eight bits

Command

Byte 1

Byte 2

Byte 3

Byte 4

Sector Lockdown

3Dh

2Ah

7Fh

30h

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