AT25DF321A datasheet(30/53 Pages) ETC2

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3686F–DFLASH–1/2014

AT25DF321A

11.

Status Register Commands

11.1

Read Status Register

The two-byte Status Register can be read to determine the device’s ready/busy status, as well as the status of many other

functions such as Hardware Locking and Software Protection. The Status Register can be read at any time, including during an

internally self-timed program or erase operation.

To read the Status Register, the CS pin must first be asserted and the opcode of 05h must be clocked into the device. After the

opcode has been clocked in, the device will begin outputting Status Register data on the SO pin during every subsequent clock

cycle. After the second byte of the Status Register has been clocked out, the sequence will repeat itself starting again with the

first byte of the Status Register as long as the CS pin remains asserted and the clock pin is being pulsed. The data in the Status

Register is constantly being updated, so each repeating sequence will output new data. The RDY/BSY status is available for

both bytes of the Status Register and is updated for each byte.

At clock frequencies above fCLK, the first two bytes of data output from the Status Register will not be valid. Therefore, if

operating at clock frequencies above fCLK, at least four bytes of data must be clocked out from the device in order to read the

correct values of both bytes of the Status Register.

Deasserting the CS pin will terminate the Read Status Register operation and put the SO pin into a high-impedance state. The

CS pin can be deasserted at any time and does not require that a full byte of data be read.

Notes:

1. Only bit 7 of Status Register Byte 1 will be modified when using the Write Status Register Byte 1 command

2. R/W = Readable and writeable

R = Readable only

Table 11-1. Status Register Format – Byte 1

Bit(1)

Name

Type(2)

Description

SPRL

Sector Protection Registers Locked

R/W

Sector Protection Registers are unlocked (default)

Sector Protection Registers are locked

RES

Reserved for future use

EPE

Erase/Program Error

Erase or program operation was successful

Erase or program error detected

WPP

Write Protect (WP) Pin Status

0WP is asserted

1WP is deasserted

3:2

SWP

Software Protection Status

All sectors are software unprotected (all Sector

Protection Registers are 0)

Some sectors are software protected. Read individual

Sector Protection Registers to determine which

sectors are protected

Reserved for future use

All sectors are software protected (all Sector

Protection Registers are 1 – default)

WEL

Write Enable Latch Status

Device is not write enabled (default)

Device is write enabled

RDY/BS

Ready/Busy Status

Device is ready

Device is busy with an internal operation

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