AT45DB641E datasheet(21/72 Pages) ETC2

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AT45DB641E

DS-45DB641E-027E–DFLASH–1/2014

Figure 7-4.

Erase Sector Protection Register

7.3.2

Program Sector Protection Register

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

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 thirty two bytes of data corresponding to Sectors 0 through 31. 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 should take place in a maximum time of t

P. During this time,

the RDY/BUSY bit in the Status Register will indicate 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 thirty two bytes, then the protection status of

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

the device, then the data will wrap back around to the beginning of the register. For instance, if thirty three

bytes of data are clocked in, then the thirty third byte will be stored at byte location 0 of the Sector Protection

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 utilizes Buffer 1 for processing. Therefore, the contents of Buffer 1

will be altered from its previous state when this command is issued.

Table 7-7.

Program Sector Protection Register Command

3Dh

2Ah

7Fh

CFh

Each transition represents eight bits

Command

Byte 1

Byte 2

Byte 3

Byte 4

Program Sector Protection Register

3Dh

2Ah

7Fh

FCh

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