AT25DF021 datasheet(15/41 Pages) ATMEL

15 / 41 page

3677D–DFLASH–04/09

AT25DF021

Registers Locked) bit of the Status Register (please refer to the Status Register description 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

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 Byte 1 command (see “Write

Status Register” on page 25 for command execution details). The Write Status Register com-

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 first byte of the Status Register. Con-

versely, to perform 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 first byte 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

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