Datasheet
2008-2018 Microchip Technology Inc. DS20002124H-page 14
24AA02E48/24AA025E48/24AA02E64/24AA025E64
9.0 PRE-PROGRAMMED EUI-48™
OR EUI-64™ NODE ADDRESS
The 24AA02XEXX is programmed at the factory with a
globally unique node address stored in the upper half
of the array and permanently write-protected. The
remaining 1,024 bits are available for application use.
FIGURE 9-1: MEMORY ORGANIZATION
9.1 EUI-48™ Node Address
(24AAXXXE48)
The 6-byte EUI-48™ node address value of the
24AAXXXE48 is stored in array locations 0xFA through
0xFF, as shown in Figure 9-2. 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.
9.1.1 ORGANIZATIONALLY UNIQUE
IDENTIFIERS (OUIs)
Each OUI provides roughly 16M (2
24
) 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).
9.1.2 EUI-64™ SUPPORT USING THE
24AAXXXE48
The pre-programmed EUI-48 node address of the
24AAXXXE48 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.
FIGURE 9-2: EUI-48 NODE ADDRESS PHYSICAL MEMORY MAP EXAMPLE (24AAXXXE48)
00h
80h
FFh
Write-Protected
Node Address Block
Standard
EEPROM
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 24AAXXXE64
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 9.2 “EUI-64™ Node Address
(24AAXXXE64)” for details.
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 After Encapsulation:
00-04-A3-FF-FE-12-34-56