AT25DF021 datasheet(12/41 Pages) ATMEL

12 / 41 page

3677D–DFLASH–04/09

AT25DF021

While the device is executing a successful erase cycle, the Status Register can be read and will

indicate that the device is busy. For faster throughput, it is recommended that the Status Regis-

ter be polled rather than waiting the tCHPE time to determine if the device has finished erasing. At

some point before the erase cycle completes, the WEL bit in the Status Register will be reset

back to the logical “0” state.

The device also incorporates an intelligent erase algorithm that can detect when a byte location

fails to erase properly. If an erase error occurs, it will be indicated by the EPE bit in the Status

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 Byte/Page Program, erase, Protect

Sector, Unprotect Sector, Program OTP Security Register, 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 com-

mand 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, and the CS pin must be deasserted on an even byte

boundary (multiples of eight bits); otherwise, the device will abort the operation and the state of

the WEL bit will not change.

Figure 9-1.

Write Enable

SCK

MSB

CCCCCCCC

OPCODE

HIGH-IMPEDANCE

SCK

MSB

00000110

OPCODE

HIGH-IMPEDANCE

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