Datasheet

2008-2013 Microchip Technology Inc. DS20002124E-page 13
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. Cur-
rently, Microchip’s OUIs are 0x0004A3 and 0x001EC0,
though this will change as addresses are exhausted.
The remaining three bytes are the Extension Identifier,
and are generated by Microchip to ensure a globally
unique, 48-bit value.
9.1.1 EUI-64™ SUPPORT USING THE
24AAXXXE48
The pre-programmed EUI-48 node address of the
24AAXXXE48 can easily be encapsulated at the appli-
cation 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: 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