AT45DB021E datasheet(24/74 Pages) DIALOG

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AT45DB021E

DS-AT45DB021E—8789J—03/2021

8.3.1

Erase Sector Protection Register

In order to modify and change the values of the Sector Protection Register, it must first be erased using the Erase

Sector Protection Register command.

To erase the Sector Protection Register, a four-byte command sequence of 3Dh, 2Ah, 7Fh, and CFh must be

clocked into the device. After the last bit of the opcode sequence has been clocked in, the CS pin must be

deasserted to initiate the internally self-timed erase cycle. The erasing of the Sector Protection Register takes

place in a maximum time of tPE. 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 erase cycle is done, then the contents of the Sector Protection

The Sector Protection Register can be erased with sector protection enabled or disabled. Since the erased state

(FFh) of each byte in the Sector Protection Register is used to indicate that a sector is specified for protection,

leaving the sector protection enabled during the erasing of the register allows the protection scheme to be more

effective in the prevention of accidental programming or erasing of the device. If an erroneous program or erase

command is sent to the device immediately after erasing the Sector Protection Register and before the register can

be reprogrammed, then the erroneous program or erase command is not processed, because all sectors are

protected.

Table 8-6.

Erase Sector Protection Register Command

Figure 8-4. Erase Sector Protection Register Timing

8.3.2

Program Sector Protection Register

Once the Sector Protection Register has been erased, it can be reprogrammed using the Program Sector

Protection Register command.

To program the Sector Protection Register, a four-byte command sequence of 3Dh, 2Ah, 7Fh, and FCh must be

clocked into the device followed by eight bytes of data corresponding to Sectors 0 through 7. After the last bit of the

opcode sequence and data have been clocked in, the CS pin must be deasserted to initiate the internally self-timed

program cycle. Programming the Sector Protection Register 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

erase cycle is done, then the contents of the Sector Protection Register cannot be guaranteed.

If the proper number of data bytes is not clocked in before the CS pin is deasserted, then the protection status of

the sectors corresponding to the bytes not clocked in cannot be guaranteed.

Example:

If only the first two bytes are clocked in instead of the complete eight bytes, then the protection status of the

last six sectors cannot be guaranteed. Furthermore, if more than eight bytes of data is clocked into the

device, the data wraps back around to the beginning of the register. For instance, if nine bytes of data are

clocked in, then the ninth byte is stored at byte location 0 of the Sector Protection Register.

Command

Byte 1

Byte 2

Byte 3

Byte 4

Erase Sector Protection Register

3Dh

2Ah

7Fh

CFh

3Dh

2Ah

7Fh

CFh

Each transition represents eight bits

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