AT45DB321E datasheet(20/73 Pages) ETC2

20 / 73 page

AT45DB321E

8784F–DFLASH–11/2013

7.3

Sector Protection Register

The nonvolatile Sector Protection Register specifies which sectors are to be protected or unprotected with either the

software or hardware controlled protection methods. The Sector Protection Register contains 64 bytes of data, of which

byte locations 0 through 63 contain values that specify whether Sectors 0 through 63 will be protected or unprotected.

The Sector Protection Register is user modifiable and must be erased before it can be reprogrammed. Table 7-4

illustrates the format of the Sector Protection Register.

Table 7-4.

Sector Protection Register

Note:

1. The default values for bytes 0 through 63 are 00h when shipped from Adesto.

Table 7-5.

Sector 0 (0a, 0b) Sector Protection Register Byte Value

Note:

1. x = Don’t care

7.3.1

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 4-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 should take place in a maximum time of

tPE. 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.

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 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 would be protected.

Table 7-6.

Erase Sector Protection Register Command

Sector Number

0 (0a, 0b)

1 to 63

Protected

See Table 7-5

FFh

Unprotected

00h

Bit 7:6

Bit 5:4

Bit 3:2

Bit 1:0

Data

Value

Sector 0a

(Page 0-7)

Sector 0b

(Page 8-127)

N/A

Sectors 0a and 0b Unprotected

0xh

Protect Sector 0a

Cxh

Protect Sector 0b

3xh

Protect Sectors 0a and 0b

Fxh

Command

Byte 1

Byte 2

Byte 3

Byte 4

Erase Sector Protection Register

3Dh

2Ah

7Fh

CFh

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