9

3387L–DFLASH–6/06

AT45DB321C

Main Memory Page Program without Built-in Erase, Page Erase, Block Erase, Main Memory

Page Program, and Auto Page Rewrite.

Bit 1 in the Status Register is used to provide information to the user whether or not the sector

protection has been enabled or disabled, either by software-controlled method or hardware-con-

trolled method. A logic 1 indicates that sector protection has been enabled and logic 0 indicates

that sector protection has been disabled.

The device density is indicated using bits 5, 4, 3, and 2 of the status register. For the

AT45DB321C, the four bits are 1,1, 0, 1. The decimal value of these four binary bits does not

equate to the device density; the four bits represent a combinational code relating to differing

densities of DataFlash devices. The device density is not the same as the density code indicated

in the JEDEC device ID information. The device density is provided only for backward

compatibility.

The result of the most recent Main Memory Page to Buffer Compare operation is indicated using

bit 6 of the status register. If bit 6 is a 0, then the data in the main memory page matches the

data in the buffer. If bit 6 is a 1, then at least one bit of the data in the main memory page does

not match the data in the buffer.

6.

Sector Protection

Two protection methods, hardware and software controlled, are provided. The selection of which

sectors to be protected/unprotected from program and erase operations is defined in the Sector

Protection Register.

6.1

Software Sector Protection

Sectors specified for protection in the Sector Protection Register can be protected from program

and erase operations by issuing the Enable Sector Protection command. To enable the sector

protection using the software controlled method, 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 command

sequence must be clocked in via the input pin (SI). After the last bit of the command sequence

has been clocked in, the CS pin must be deasserted after which the sector protection will be

enabled.

To disable the sector protection using the software controlled method, 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 sequence for the Disable Sector Protection command must be clocked in via

the input pin (SI). After the last bit of the command sequence has been clocked in, the CS pin

must be deasserted after which the sector protection will be disabled. The Disable Sector Pro-

tection command is ignored while the WP pin is asserted.

Table 5-2.

Status Register Format

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

RDY/BUSY

COMP

1

1

0

1

Protect

X

Command

Byte 1

Byte 2

Byte 3

Byte 4

Enable Sector Protection

3DH

2AH

7FH

A9H

Disable Sector Protection

3DH

2AH

7FH

9AH

Read Sector Protection Register

32H

00H

00H

00H