AT45DB021D_13 datasheet(13/48 Pages) ETC2

13 / 48 page

3638M–DFLASH–5/2013

AT45DB021D

7.1.1

Erase Sector Protection Register Command

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, the CS pin must first be asserted as it would be with any other command.

Once the CS pin has been asserted, the appropriate 4-byte opcode sequence must be clocked into the device via

the SI pin. The 4-byte opcode sequence must start with 3DH and be followed by 2AH, 7FH, and CFH. 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 should take place in a time of tPE, during which time 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.

The Sector Protection Register can be erased with the 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 for some reason an

erroneous program or erase command is sent to the device immediately after erasing the Sector Protection

processed because all sectors would be protected.

Table 7-4.

Erase Sector Protection Register Command

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 the appropriate 4-byte opcode

sequence must be clocked into the device via the SI pin. The 4-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 4-bytes of data, so 4-bytes must be clocked into the device. The first byte of data

corresponds to sector zero, the second byte corresponds to sector one, the third byte corresponds to sector two,

and the last byte of data corresponding to sector three.

After the last data byte has 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 time of tP, during which

time the Status Register will indicate that the device is busy. If the device is powered-down during the program

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 can not be guaranteed. For example, if only the first two bytes

are clocked in instead of the complete 8-bytes, then the protection status of the last six sectors cannot be

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

Each transition

represents 8 bits

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