25AA02E48 datasheet(13/26 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS22123B-page 13

25AA02E48

3.0

PRE-PROGRAMMED EUI-48™

NODE ADDRESS

The 25AA02E48 is programmed at the factory with a

globally unique, EUI-48™ and EUI-64™ compatible

node address stored in the upper 1/4 of the array and

write-protected through the STATUS register. The

remaining 1,536 bits are available for application use.

FIGURE 3-1:

MEMORY ORGANIZATION

The 6-byte EUI-48™ node address value is stored in

array locations 0xFA through 0xFF, as shown in

Figure 3-2. The first 3 bytes are the Organizationally

Unique Identifier (OUI) assigned to Microchip by the

IEEE Registration Authority. Microchip’s OUI is

0x0004A3. The remaining 3 bytes are the Extension

Identifier, and are generated by Microchip to ensure a

globally-unique, 48-bit value.

3.1

EUI-64™ Support

The pre-programmed EUI-48 node address can easily

be encapsulated at the application level to form a glob-

ally unique, 64-bit node address for systems utilizing

the EUI-64 standard. This is done by adding 0xFFFE

between the OUI and the Extension Identifier, as

shown below.

FIGURE 3-2:

EUI-48 NODE ADDRESS PHYSICAL MEMORY MAP EXAMPLE

3.2

Factory-Programmed Write

Protection

In order to help guard against accidental corruption of

the EUI-48 node address, the BP1 and BP0 bits of the

STATUS register are programmed at the factory to ‘0’

and ‘1’, respectively, as shown in the following table:

This protects the upper 1/4 of the array (0xC0 to 0xFF)

from write operations. This array block can be utilized

for writing by clearing the BP bits with a Write Status

formed, care must be taken to prevent overwriting the

EUI-48 value.

00h

C0h

FFh

Write-Protected

EUI-48™ Block

Standard

EEPROM

FAh

FFh

24-bit Organizationally

Unique Identifier

24-bit Extension

Identifier

00h

04h

A3h

12h

34h

56h

Corresponding EUI-48™ Node Address: 00-04-A3-12-34-56

Description

Data

Array

Address

Corresponding EUI-64™ Node Address: 00-04-A3-FF-FE-12-34-56

7654

XXXX

BP1

BP0

WEL

WIP

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