AT25DF081A datasheet(22/54 Pages) ETC2

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8715C–SFLSH–1/2013

AT25DF081A

Essentially, if the SPRL bit of the Status Register is in the logical “0” state (Sector Protection Registers are not

locked), then writing a 00h to the first byte of the Status Register will perform a Global Unprotect without changing

the state of the SPRL bit. Similarly, writing a 7Fh to the first byte of the Status Register will perform a Global Protect

and keep the SPRL bit in the logical “0” state. The SPRL bit can, of course, be changed to a logical “1” by writing an

FFh if software-locking or hardware-locking is desired along with the Global Protect.

If the desire is to only change the SPRL bit without performing a Global Protect or Global Unprotect, then the sys-

tem can simply write a 0Fh to the first byte of 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 first byte of the Status Register, bits five, four, three, and two 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

seven, the SPRL bit, will actually be modified. Therefore, when reading the first byte of the Status Register, bits

five, four, three, and two 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 “Read Status Register” on page 31 and Table 11-1 on page 31 for

details on the Status Register format and what values can be read for bits five, four, three, and two.

0 x 0 0 0 0 x x

0 x 0 0 0 1 x x

0 x 1 1 1 0 x x

0 x 1 1 1 1 x x

1 x 0 0 0 0 x x

1 x 0 0 0 1 x x

1 x 1 1 1 0 x x

1 x 1 1 1 1 x x

No change to the current protection level. All sectors currently protected will remain

protected, and all sectors currently unprotected will remain unprotected.

The Sector Protection Registers are soft-locked and cannot be changed when the

current state of SPRL is 1. Therefore, a Global Protect/Unprotect will not occur.

However, the SPRL bit can be changed back to a 0 from a 1 since the WP pin is

HIGH. To perform a Global Protect/Unprotect, the Write Status Register command

must be issued again after the SPRL bit has been changed from a 1 to a 0.

Table 9-2.

Valid SPRL and Global Protect/Unprotect Conditions (Continued)

State

Current

SPRL

Value

New Write Status

Data

Protection Operation

New

SPRL

Value

Bit

7 6 5 4 3 2 1 0

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