AT45DB021E datasheet(24/69 Pages) RENESAS

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DS-AT45DB021E-8789 Rev. N

Page 24

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AT45DB021E Datasheet

9.3.2

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 4-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. The programming of the Sector Protection Register must take 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 completion of the erase cycle, 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,

then 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.

The data bytes clocked into the Sector Protection Register need to be valid values (0Xh, 3Xh, CXh, and FXh for

Sector 0a or Sector 0b, and 00h or FFh for other sectors) in order for the protection to function correctly. If a non-

valid value is clocked into a byte location of the Sector Protection Register, then the protection status of the sector

corresponding to that byte location cannot be guaranteed.

Example: If a value of 17h is clocked into byte location 2 of the Sector Protection Register, then the protection

status of Sector 2 cannot be guaranteed.

The Sector Protection Register can be reprogrammed while the sector protection is enabled or disabled. Being

able to reprogram the Sector Protection Register with the sector protection enabled allows the user to temporarily

disable the sector protection to an individual sector rather than disabling sector protection completely.

The Program Sector Protection Register command uses the internal buffer for processing. Therefore, the contents

of the Buffer is altered from its previous state when this command is issued.

Table 11. Program Sector Protection Register Command

Figure 9. Program Sector Protection Register

Command

Byte 1

Byte 2

Byte 3

Byte 4

Program Sector Protection Register

3Dh

2Ah

7Fh

FCh

Data Byte

3Dh

2Ah

7Fh

FCh

Data Byte

n + 1

Each transition represents eight bits

Data Byte

n + 7

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