AT25DF256 datasheet(28/47 Pages) RENESAS

28 / 47 page

DS-AT25DF256-035 Rev.G

Page 28

2024-01-08

AT25DF256 Datasheet

Figure 21. Read Manufacturer and Device ID

12.2 Read ID (Legacy Command)

Identification information can be read from the device to enable systems to electronically query and identify the

device while it is in system. The preferred method for doing so is the JEDEC standard method described in

Section 12.1; however, the legacy Read ID command is supported on the AT25DF256 to enable backwards

compatibility to previous generation devices.

To read the identification information, the CS pin must first be asserted and the opcode of 15h must be clocked

into the device. After the opcode has been clocked in, the device begins outputting the identification data on the

SO pin during the subsequent clock cycles. The first byte output is the Manufacturer ID of 1Fh followed by a single

byte of data representing a device code of 65h. After the device code is output, the SO pin goes into a high-

impedance state; thus, additional clock cycles have no affect on the SO pin, and no data are output.

Deasserting the CS pin stops the Read ID operation and puts 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 read.

Figure 22. Read ID (Legacy Command)

SCK

9Fh

OPCODE

1Fh

42h

00h

MANUFACTURER ID

DEVICE ID

BYTE1

DEVICE ID

BYTE2

EXTENDED

DEVICE

INFORMATION

STRING LENGTH

HIGH-IMPEDANCE

Note: Each transition

shown for SI and SO represents one byte (8 bits)

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