AT25DF641A datasheet(41/57 Pages) ATMEL

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8693A–DFLASH–8/10

Atmel AT25DF641A [Preliminary]

Figure 12-1. Reset

12.2

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 ven-

dor specific Extended Device Information.

The Read Manufacturer and Device ID command is limited to a maximum clock frequency of

CLK. Since not all Flash devices are capable of operating at very high clock frequencies, applica-

tions should be designed to read the identification information from the devices at a reasonably

low clock frequency to ensure that all devices to be used in the application can be identified

properly. Once the identification process is complete, the application can then 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 out-

putting 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 (EDI) String Length, which will be

01h indicating that one byte of EDI data follows. After the one byte of EDI data 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 EDI

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.

SCK

MSB

1111000

OPCODE

CONFIRMATION BYTE IN

10 11

814 15

MSB

110100

HIGH-IMPEDANCE

AT25DF641A Datasheet(PDF) 41 Page - ATMEL Corporation