22

AT25DF256

DS-25DF256–035D–2/2017

12.

Other Commands and Functions

12.1 Read Manufacturer and Device ID

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

while it is in system. The identification method and the command opcode comply with the JEDEC standard for

“Manufacturer and Device ID Read Methodology for SPI Compatible Serial Interface Memory Devices”. The type of

information that can be read from the device includes the JEDEC defined Manufacturer ID, the vendor specific Device ID,

and the vendor specific Extended Device Information.

Since not all Flash devices are capable of operating at very high clock frequencies, applications should be designed to

read the identification information from the devices at a reasonably low clock frequency to ensure all devices used in the

application can be identified properly. Once the identification process is complete, the application can increase the clock

frequency to accommodate specific Flash devices that are capable of operating at the higher clock frequencies.

To read the identification information, the CS pin must first be asserted and the opcode of 9Fh 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 followed by two bytes of Device

ID information. The fourth byte output will be the Extended Device Information String Length, which will be 00h indicating

that no Extended Device Information follows. After the Extended Device Information String Length byte 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. As indicated in the JEDEC standard, reading the Extended Device Information String Length and any

subsequent data is optional.Deasserting the CS pin will terminate the Manufacturer and Device ID 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.

Table 12-1. Manufacturer and Device ID Information

Byte No.

Data Type

Value

1

Manufacturer ID

1Fh

2

Device ID (Part 1)

40h

3

Device ID (Part 2)

00h

4

Extended Device Information String Length

00h

Table 12-2. Manufacturer and Device ID Details

Data Type

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Hex

Value

Details

Manufacturer ID

JEDEC Assigned Code

1Fh

JEDEC Code: 0001 1111 (1Fh for Adesto)

0

0

0

1

1

1

1

1

Device ID (Part

1)

Family Code

Density Code

40h

Family Code: 010 (AT25F/AT25FSxxx series)

Density Code: 00000 (256-Kbit)

0

1

0

0

0

0

0

0

Device ID (Part

2)

Sub Code

Product Version Code

00h

Sub Code:

000 (Standard series)

Product Version:00000

0

0

0

0

0

0

0

0