AT25DF641_13 datasheet(27/56 Pages) ETC2

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AT25DF641

3680F–DFLASH–4/10

Figure 8-5.

Read Sector Protection Register

SCK

MS B

10 11

37 38

31 32

29 30

39 40

OP C ODE

MS B

ADDR E S S B ITS A23-A0

DATA B Y TE

HIG H-IMP E DANC E

8.7.

Protected States and the Write Protect (

) Pin

The

pin is not linked to the memory array itself and has no direct effect on the protection status or lockdown

status of the memory array. Instead, the

pin, in conjunction with the SPRL (Sector Protection Registers

Locked) bit in the Status Register, is used to control the hardware locking mechanism of the device. For hardware

locking to be active, two conditions must be met-the

pin must be asserted and the SPRL bit must be in the

logical “1” state.

When hardware locking is active, the Sector Protection Registers are locked and the SPRL bit itself is also locked.

Therefore, sectors that are protected will be locked in the protected state, and sectors that are unprotected will be

locked in the unprotected state. These states cannot be changed as long as hardware locking is active, so the

Protect Sector, Unprotect Sector, and Write Status Register commands will be ignored. In order to modify the

protection status of a sector, the

pin must first be deasserted, and the SPRL bit in the Status Register must be

reset back to the logical “0” state using the Write Status Register command. When resetting the SPRL bit back to

a logical “0”, it is not possible to perform a Global Protect or Global Unprotect at the same time since the Sector

Protection Registers remain soft-locked until after the Write Status Register command has been executed.

If the

pin is permanently connected to GND, then once the SPRL bit is set to a logical “1”, the only way to

reset the bit back to the logical “0” state is to power-cycle the device. This allows a system to power-up with all

sectors software protected but not hardware locked. Therefore, sectors can be unprotected and protected as

needed and then hardware locked at a later time by simply setting the SPRL bit in the Status Register.

When the

pin is deasserted, or if the

pin is permanently connected to VCC, the SPRL bit in the Status

ability to prevent erroneous Protect Sector or Unprotect Sector commands from being processed. When changing

the SPRL bit to a logical “1” from a logical “0”, it is also possible to perform a Global Protect or Global Unprotect at

the same time by writing the appropriate values into bits five, four, three, and two of the first byte of the Status

Table 8-4 and Table 8-5 detail the various protection and locking states of the device.

Table 8-4.

Sector Protection Register States

Sector Protection Register

(1)Error! Reference source not found.

Sector

(1)

(Don't Care)

Unprotected

Protected

Note: 1. “n” represents a sector number.

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