AT25DF021A-MHNHR-T datasheet(27/59 Pages) RENESAS

27 / 59 page

DS-AT25DF021A-042 Rev. L

Page 27

8/7/23

AT25DF021A Datasheet

to a logical 1 without affecting the current sector protection status (no changes are made to the Sector Protection

Registers).

When writing to the Status Register, bits 5, 4, 3, and 2 are not actually modified but are decoded by the device for

the purposes of the Global Protect and Global Unprotect functions. Only bit 7, the SPRL bit, is modified. Thus,

when reading the Status Register, bits 5, 4, 3, and 2 do not reflect the values written to them but instead indicate

the status of the WP pin and the sector protection status. See the “Read Status Register” section and Table 9 on

page 31 for details on the Status Register format and what values can be read for bits 5, 4, 3, and 2.

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, does 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 begins outputting

data on the SO pin during every subsequent clock cycle. The data being output are a repeating byte of either FFh

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

Deasserting the CS pin stops 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) bit in the

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

“Status Register Commands” on page 31 for more details).

Figure 23. Read Sector Protection Register

Table 5. 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

DDDDDDDD

ADDRESS BITS A23-A0

DATA BYTE

HIGH-IMPEDANCE

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