MCP79520 datasheet(45/58 Pages) MICROCHIP

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DS20002300D-page 45

MCP7951X/MCP7952X

6.5

Preprogrammed EUI-48™ or

EUI-64™ Node Address

The MCP795X1 and MCP795X2 are programmed at

the factory with a globally unique node address stored

in the protected EEPROM block.

6.5.1

EUI-48 NODE ADDRESS

(MCP795X1)

The 6-byte EUI-48 node address value of the

MCP795X1 is stored in protected EEPROM locations

0x02 through 0x07, as shown in Figure 6-13. The first

three bytes are the Organizationally Unique Identifier

(OUI) assigned to Microchip by the IEEE Registration

Authority. The remaining three bytes are the Extension

Identifier and are generated by Microchip to ensure a

globally-unique, 48-bit value.

6.5.1.1

Organizationally Unique Identifiers

(OUIs)

Each OUI provides roughly 16M (224) addresses. Once

the address pool for an OUI is exhausted, Microchip

will acquire a new OUI from IEEE to use for

programming this model. For more information on past

and current OUIs see “Organizationally Unique

Identifiers For Preprogrammed EUI-48 and EUI-64

Address Devices” Technical Brief (DS90003187).

6.5.1.2

EUI-64 Support Using the

MCP795X1

The preprogrammed EUI-48 node address of the

MCP795X1 can easily be encapsulated at the

application level to form a globally 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.

6.5.2

EUI-64 NODE ADDRESS

(MCP795X2)

The 8-byte EUI-64™ node address value of the

MCP795X2 is stored in array locations 0x00 through

0x07, as shown in Figure 6-14. The first three bytes are

the Organizationally Unique Identifier (OUI) assigned

to Microchip by the IEEE Registration Authority.

The remaining five bytes are the Extension Identifier,

and are generated by Microchip to ensure a

globally-unique, 64-bit value..

FIGURE 6-13:

EUI-48 NODE ADDRESS PHYSICAL MEMORY MAP EXAMPLE (MCP795X1)

Note:

The OUI will change as addresses are

exhausted. Customers are not guaran-

teed to receive a specific OUI and should

design their application to accept new

OUIs as they are introduced.

Note:

As an alternative, the MCP795X2 features

an EUI-64 node address that can be used

in EUI-64 applications directly without the

need

for

encapsulation,

thereby

simplifying

system

software.

See

Section 6.5.2 “EUI-64 Node Address

(MCP795X2)” for details.

Note:

In conformance with IEEE guidelines,

Microchip will not use the values 0xFFFE

and 0xFFFF for the first two bytes of the

EUI-64 Extension Identifier. These two

values are specifically reserved to allow

applications

encapsulate

EUI-48

addresses into EUI-64 addresses.

02h

07h

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 After Encapsulation: 00-04-A3-FF-FE-12-34-56

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