23

AT25DF256

DS-25DF256–035D–2/2017

Figure 12-1. 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 “Read Manufacturer and Device ID”

method described in Section 12.1 on page 22; 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 will begin outputting the identification data on the SO pin during

the subsequent clock cycles. The first byte that will be output will be 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 will go into a high-impedance state;

therefore, additional clock cycles will have no affect on the SO pin and no data will be output.

Deasserting the CS pin will terminate the Read ID 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 read.

Figure 12-2. Read ID (Legacy Command)

12.3 Deep Power-Down

During normal operation, the device will be placed in the standby mode to consume less power as long as the CS pin

remains deasserted and no internal operation is in progress. The Deep Power-Down command offers the ability to place

the device into an even lower power consumption state called the Deep Power-Down mode.

SCK

CS

SI

SO

6

0

9Fh

8

7

38

OPCODE

1Fh

40h

00h

00h

MANUFACTURER ID

DEVICE ID

BYTE1

DEVICE ID

BYTE2

EXTENDED

DEVICE

INFORMATION

STRING LENGTH

HIGH-IMPEDANCE

14

16

15

22

24

23

30

32

31

Note: Each transition

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