AT25DF321 datasheet(15/37 Pages) ATMEL

15 / 37 page

3669A–DFLASH–07/07

AT25DF321

As a safeguard against accidental or erroneous locking or unlocking of sectors, the Sector Pro-

tection Registers can themselves be locked from updates by using the SPRL (Sector Protection

Registers Locked) bit of the Status Register (please refer to “Status Register Commands” on

page 20 for more details). If the Sector Protection Registers are locked, then any attempts to

issue the Unprotect Sector command will be ignored, and the device will reset the WEL bit in the

Status Register back to a logical “0” and return to the idle state once the CS pin has been

deasserted.

Figure 9-4.

Unprotect Sector

9.5

Global Protect/Unprotect

The Global Protect and Global Unprotect features can work in conjunction with the Protect Sec-

tor and Unprotect Sector functions. For example, a system can globally protect the entire

memory array and then use the Unprotect Sector command to individually unprotect certain sec-

tors and individually reprotect them later by using the Protect Sector command. Likewise, a

system can globally unprotect the entire memory array and then individually protect certain sec-

tors as needed.

Performing a Global Protect or Global Unprotect is accomplished by writing a certain combina-

tion of data to the Status Register using the Write Status Register command (see “Write Status

mand is also used to modify the SPRL (Sector Protection Registers Locked) bit to control

hardware and software locking.

To perform a Global Protect, the appropriate WP pin and SPRL conditions must be met and the

system must write a logical “1” to bits 5, 4, 3, and 2 of the Status Register. Conversely, to per-

form a Global Unprotect, the same WP and SPRL conditions must be met but the system must

write a logical “0” to bits 5, 4, 3, and 2 of the Status Register. Table 9-2 details the conditions

necessary for a Global Protect or Global Unprotect to be performed.

SCK

MSB

00111001

410 11

812

29 30

27 28

OPCODE

AAAA

AAA

ADDRESS BITS A23-A0

HIGH-IMPEDANCE

AT25DF321 Datasheet(PDF) 15 Page - ATMEL Corporation