11

3633C–DFLASH–08/06

AT26DF321 [Preliminary]

Figure 8-4.

Chip Erase

9.

Protection Commands and Features

9.1

Write Enable

The Write Enable command is used to set the Write Enable Latch (WEL) bit in the Status Regis-

ter to a logical “1” state. The WEL bit must be set before a program, erase, Protect Sector,

Unprotect Sector, or Write Status Register command can be executed. This makes the issuance

of these commands a two step process, thereby reducing the chances of a command being

accidentally or erroneously executed. If the WEL bit in the Status Register is not set prior to the

issuance of one of these commands, then the command will not be executed.

To issue the Write Enable command, the CS pin must first be asserted and the opcode of 06h

must be clocked into the device. No address bytes need to be clocked into the device, and any

data clocked in after the opcode will be ignored. When the CS pin is deasserted, the WEL bit in

the Status Register will be set to a logical “1”. The complete opcode must be clocked into the

device before the CS pin is deasserted; otherwise, the device will abort the operation and the

state of the WEL bit will not change.

Figure 9-1.

Write Enable

SCK

CS

SI

SO

MSB

23

1

0

CCCCCCCC

67

5

4

OPCODE

HIGH-IMPEDANCE

SCK

CS

SI

SO

MSB

23

1

0

00000110

67

5

4

OPCODE

HIGH-IMPEDANCE