AT45DB321C datasheet(8/37 Pages) ATMEL

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AT45DB321C [Preliminary]

3387B–DFLSH–9/04

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.

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 com-

mand. 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 Protection command is ignored while the WP pin is

asserted.

Software Sector Protection is useful in applications in which the WP pin is not or cannot

be controlled by a host processor. In such instances, the WP pin may be left floating (the

WP pin is pulled high internally) and sector protection can be controlled using the soft-

ware commands.

If the device is power cycled, then the Software Sector Protection will be disabled. Once

the device is powered up, the Enable Sector Protection command should be reissued if

sector protection is desired and if the WP pin is not used. The RESET pin has no effect

on the Software Sector Protection.

HARDWARE SECTOR PROTECTION: Sectors specified for protection in Sector Pro-

tection Register can be protected from program and erase operations by utilizing the

Write Protection (WP) pin. The protection can be enabled by asserting the WP pin and

keeping the pin in its asserted state. Any sector specified for protection cannot be

erased or reprogrammed as long as the WP pin is asserted. The protection can be dis-

abled by deasserting the WP pin high. A filter is provided on the WP pin to help protect

against spurious noise on the WP pin. Hardware Sector Protection will provide continu-

ous protection, based on the contents of the Sector Protection Register, in an

application where WP is always driven low. Please read the description of the WP pin on

page 13 for more information.

SECTOR PROTECTION REGISTER: Sector Protection Register is a nonvolatile regis-

ter that contains 16 bytes of data, as shown below:

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

Sector Number

0 (0a, 0b)

1 to 15

Protected

See Below

FFH

Unprotected

00H

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