25AA02E48 Datasheet, PDF (7/20 Pages) Microchip Technology – 2K SPI Bus Serial EEPROM with EUI-48™ Node Identity

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
00h
Standard
EEPROM
C0h
Write-Protected
EUI-48™ Block _FFh
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. 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
Description
24-bit Organizationally
Unique Identifier
Data
00h
04h
A3h
Array
Address
FAh
24-bit Extension
Identifier
12h
34h
56h
FFh
Corresponding EUI-48™ Node Address: 00-04-A3-12-34-56
Corresponding EUI-64™ Node Address: 00-04-A3-FF-FE-12-34-56
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:
7654 3
2
1
0
X X X X BP1 BP0 WEL WIP
———— 0
1
—
—
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
Register (WRSR) instruction. Note that if this is per-
formed, care must be taken to prevent overwriting the
EUI-48 value.
© 2008 Microchip Technology Inc.
Preliminary
DS22123A-page 7