11

3387L–DFLASH–6/06

AT45DB321C

6.3.1

Erasing the Sector Protection Register

To erase the Sector Protection Register, the CS pin must first be asserted. Once the CS pin has

been asserted, the 4-byte erase command sequence must be clocked in via the SI (serial input)

pin. After the last bit of the command sequence has been clocked in, the CS pin must be deas-

serted to initiate the internally self-timed erase cycle (t

that the device is busy during the erase cycle. The erased state of each bit (of a byte) in the Sec-

tor Protection Register indicates that the corresponding sector is flagged for protection. The

RESET pin is disabled during this erase cycle to prevent incomplete erasure of the Sector Pro-

tection Register.

6.3.2

Programming the Sector Protection Register

To program the Sector Protection Register, the CS pin must first be asserted. Once the CS pin

has been asserted, the 4-byte command sequence must be clocked in via the SI (serial input)

pin. After the last bit of the command sequence has been clocked in, the data for the contents of

the Sector Protection Register must be clocked in. The first byte corresponds to sector 0 (0a,

0b), the second byte corresponds to Sector 1 and the last byte (byte 16) corresponds to Sector

15. After the last bit of data has been clocked in, the CS pin must be deasserted to initiate the

internally self-timed program cycle (t

busy during the program cycle. The RESET pin is disabled during this program cycle to prevent

incomplete programming of the sector protection register.

6.3.3

Reading the Sector Protection Register

To read the Sector Protection Register, the CS pin must first be asserted. Once the CS pin has

been asserted, a 4-byte command sequence 32H, 00H, 00H, 00H and 32 don’t care clock cycles

must be clocked in via the SI (serial input) pin. The 32 don’t care clock cycles are required to ini-

tialize the read operation. After the 32 don’t care clock cycles, any additional clock pulses on the

SCK pin will result in data being output on the SO (serial output) pin. The read will begin with

Byte_1 of the Sector Protection Register for Sector_0, followed with Byte_2 for Sector_1. The

read operation will continue until Byte_16 for Sector_15 is read. Once the last byte is read a low-

to-high transition on the CS pin is required to terminate the read operation.

Note:

Next generation devices of the “D” family will not require the 32 don’t care clock cycles.

Command

Byte 1

Byte 2

Byte 3

Byte 4

Erase Sector Protection Register

3DH

2AH

7FH

CFH

Command

Byte 1

Byte 2

Byte 3

Byte 4

Program Sector Protection Register

3DH

2AH

7FH

FCH

Command

Byte 1

Byte 2

Byte 3

Byte 4

Read Sector Protection Register

32H

00H

00H

00H