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AT45DB321D [DATASHEET]

3597T–DFLASH–11/2013

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 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 for some reason 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 will not be processed because all sectors will be protected.

Table 7-4.

Erase Sector Protection Register Command

Command

Byte 1

Byte 2

Byte 3

Byte 4

Figure 7-2. Erase Sector Protection Register

7.1.2

Program Sector Protection Register Command

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, the CS pin must first be asserted, and then the appropriate four-byte opcode

sequence must be clocked into the device via the SI pin. The four-byte opcode sequence must start with 3DH, and be followed

by 2AH, 7FH, and FCH. After the last bit of the opcode sequence has been clocked into the device, the data for the contents of

the sector protection register must be clocked in. As described in Section 7.1, the sector protection register contains 64 bytes of

data, and so 64 bytes must be clocked into the device. The first byte of data corresponds to sector 0, the second byte

corresponds to sector 1, and so on, with the last byte of data corresponding to sector 63.

After the last data byte has been clocked in, the CS pin must be deasserted to initiate the internally self-timed program cycle.

will indicate that the device is busy. If the device is powered down during the program cycle, 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 can not be guaranteed. For example, if only the first two bytes are clocked in instead

of the complete 62 bytes, then the protection status of the last 62 sectors cannot be guaranteed. Furthermore, if more than 64

bytes of data are clocked into the device, then the data will wrap back around to the beginning of the register. For instance, if 65

If a value other than 00H or FFH 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. For 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 sector protection is enabled or disabled. Being able to reprogram the

sector protection register with sector protection enabled allows the user to temporarily disable the sector protection of an

individual sector rather than disabling sector protection completely.

The program sector protection register command utilizes the internal SRAM buffer 1 for processing. Therefore, the contents of

buffer 1 will be altered from its previous state when this command is issued.

Table 7-5.

Program Sector Protection Register Command

Command

Byte 1

Byte 2

Byte 3

Byte 4

Erase sector protection register

3DH

2AH

7FH

CFH

Opcode

byte 1

Opcode

byte 2

Opcode

byte 3

Opcode

byte 4

CS

Each transition

represents 8 bits

SI

Program sector protection register

3DH

2AH

7FH

FCH