AT25DF081A datasheet(23/54 Pages) ETC2

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8715C–SFLSH–1/2013

AT25DF081A

9.6

Read Sector Protection Registers

The Sector Protection Registers can be read to determine the current software protection status of each sector.

Reading the Sector Protection Registers, however, will not determine the status of the WP pin.

To read the Sector Protection Register for a particular sector, the CS pin must first be asserted and the opcode of

3Ch must be clocked in. Once the opcode has been clocked in, three address bytes designating any address

within the sector must be clocked in. After the last address byte has been clocked in, the device will begin output-

ting data on the SO pin during every subsequent clock cycle. The data being output will be a repeating byte of

either FFh or 00h to denote the value of the appropriate Sector Protection Register.

At clock frequencies above fCLK, the first byte of data output will not be valid. Therefore, if operating at clock fre-

quencies above fCLK, at least two bytes of data must be clocked out from the device in order to determine the

correct status of the appropriate Sector Protection Register.

Deasserting the CS pin will terminate the read 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.

In addition to reading the individual Sector Protection Registers, the Software Protection Status (SWP) bits in the

Status Register can be read to determine if all, some, or none of the sectors are software protected (refer to “Read

Status Register” on page 31 for more details).

Figure 9-5.

Read Sector Protection Register

Table 9-3.

Read Sector Protection Register – Output Data

Output Data

Sector Protection Register Value

00h

Sector Protection Register value is 0 (sector is unprotected)

FFh

Sector Protection Register value is 1 (sector is protected)

SCK

MSB

00111100

410 11

812

37 38

31 32

29 30

39 40

OPCODE

AAAA

AAA

MSB

DDDDDDD

ADDRESS BITS A23-A0

DATA BYTE

HIGH-IMPEDANCE

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