17

3669B–DFLASH–6/09

AT25DF321

If the desire is to only change the SPRL bit without performing a Global Protect or Global Unpro-

tect, then the system can simply write a 0Fh to the Status Register to change the SPRL bit from

a logical “1” to a logical “0” provided the WP pin is deasserted. Likewise, the system can write an

F0h to change the SPRL bit from a logical “0” to a logical “1” without affecting the current sector

protection status (no changes will be made to the Sector Protection Registers).

When writing to the Status Register, bits 5, 4, 3, and 2 will not actually be modified but will be

decoded by the device for the purposes of the Global Protect and Global Unprotect functions.

Only bit 7, the SPRL bit, will actually be modified. Therefore, when reading the Status Register,

bits 5, 4, 3, and 2 will not reflect the values written to them but will instead indicate the status of

the WP pin and the sector protection status. Please refer to the “Read Status Register” section

and Table 10-1 on page 20 for details on the Status Register format and what values can be

read for bits 5, 4, 3, and 2.

9.6

Read Sector Protection Registers

The Sector Protection Registers can be read to determine the current software protection status

of each sector. Reading the Sector Protection Registers, however, will not determine the status

of the WP pin.

To read the Sector Protection Register for a particular sector, the CS pin must first be asserted

and the opcode of 3Ch must be clocked in. Once the opcode has been clocked in, three address

bytes designating any address within the sector must be clocked in. After the last address byte

has been clocked in, the device will begin outputting data on the SO pin during every subse-

quent clock cycle. The data being output will be a repeating byte of either FFh or 00h to denote

the value of the appropriate Sector Protection Register

Deasserting the CS pin will terminate the read operation and put the SO pin into a high-imped-

ance state. The CS pin can be deasserted at any time and does not require that a full byte of

data be read.

In addition to reading the individual Sector Protection Registers, the Software Protection Status

(SWP) bit in the Status Register can be read to determine if all, some, or none of the sectors are

software protected (please refer to “Status Register Commands” on page 20 for more details).

Table 9-3.

Read Sector Protection Register – Output Data

Output Data

Sector Protection Register Value

00h

Sector Protection Register value is 0 (sector is unprotected).

FFh

Sector Protection Register value is 1 (sector is protected).