13

3633C–DFLASH–08/06

AT26DF321 [Preliminary]

and erase operations. In addition, the WEL bit in the Status Register will be reset back to the log-

ical “0” state.

The complete three address bytes must be clocked into the device before the CS pin is deas-

serted; otherwise, the device will abort the operation, the state of the Sector Protection Register

will be unchanged, and the WEL bit in the Status Register will be reset to a logical “0”.

As a safeguard against accidental or erroneous protecting or unprotecting of sectors, the Sector

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

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

on page 19 for more details). If the Sector Protection Registers are locked, then any attempts to

issue the Protect 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 9-3.

Protect Sector

9.4

Unprotect Sector

Issuing the Unprotect Sector command to a particular sector address will reset the correspond-

ing Sector Protection Register to the logical “0” state (see Table 9-1 on page 12 for Sector

Protection Register values). Every physical sector of the device has a corresponding single-bit

Sector Protection Register that is used to control the software protection of a sector.

Before the Unprotect Sector command can be issued, the Write Enable command must have

been previously issued to set the WEL bit in the Status Register to a logical “1”. To issue the

Unprotect Sector command, the CS pin must first be asserted and the opcode of 39h must be

clocked into the device. After the opcode has been clocked in, the three address bytes designat-

ing any address within the sector to be unlocked must be clocked in. Any additional data clocked

into the device after the address bytes will be ignored. When the CS pin is deasserted, the Sec-

tor Protection Register corresponding to the sector addressed by A23-A0 will be reset to the

logical “0” state, and the sector itself will be unprotected. In addition, the WEL bit in the Status

Register will be reset back to the logical “0” state.

The complete three address bytes must be clocked into the device before the CS pin is deas-

serted; otherwise, the device will abort the operation, the state of the Sector Protection Register

will be unchanged, and the WEL bit in the Status Register will be reset to a logical “0”.

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

SCK

CS

SI

SO

MSB

MSB

23

1

0

00110110

67

5

410 11

9

812

31

29 30

27 28

26

OPCODE

AAAA

AAA

A

A

A

A

A

ADDRESS BITS A23-A0

HIGH-IMPEDANCE