25CSM04 datasheet(40/55 Pages) MICROCHIP

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25CSM04

DS20005817D-page 40

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11.0 IDENTIFICATION REGISTER

The Identification register contains identification

information that can be read from the device to enable

systems to electronically query and identify the

25CSM04 while it is in system.

The identification method and the instruction 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 (EDI).

11.1

Reading the Identification

To read the identification information, the CS pin must

first be asserted and the 9Fh opcode (SPID) 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 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, for the

25CSM04, will be 01h indicating one byte of EDI data

follows.

After one byte of EDI data is output, the SO pin will go

into a high-impedance state; therefore, additional clock

cycles will have no effect 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 sequence 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. This sequence is depicted in Figure 11-1.

FIGURE 11-1:

READ IDENTIFICATION REGISTER (SPID) SEQUENCE

MANUFACTURER AND DEVICE ID DETAILS

Data Type

Byte

No.

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Hex

Value

Details

Manufacturer ID

JEDEC® Assigned Code

29h

JEDEC® Code: 0010 1001

(29h for Microchip)

101

001

Device ID (Part 1)

Family Code

Density Code

001

100

CCh

4-Mbit Density Code

Device ID (Part 2)

Sub Code

Product Variant

000

00h

Reserved for Future Use

EDI Length

000

001

01h

Indicates one EDI byte

EDI Byte 1

Device Revision

000

00h

First generation, SPI 4-Mbit

device

SCK

SPID Opcode

9Fh

High-Impedance

29h

CCh

00h

01h

00h

Manufacturer

Device ID

Byte 1

Device ID

Byte 2

EDI

String

EDI Data

Byte 1

Note:

Each transition

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

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