25AA02E48 Microchip Technology, 25AA02E48 Datasheet - Page 13

• Manufacturer Part Number: 25AA02E48
• Description: 2K SPI Bus Serial EEPROM
• Manufacturer: Microchip Technology

3.0
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:
FIGURE 3-2:
3.2
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
Register (WRSR) instruction. Note that if this is per-
formed, care must be taken to prevent overwriting the
EUI-48 value.
 2010 Microchip Technology Inc.
—
X
7
Corresponding EUI-48™ Node Address: 00-04-A3-12-34-56
Corresponding EUI-64™ Node Address: 00-04-A3-FF-FE-12-34-56
—
X
6
Description
Address
PRE-PROGRAMMED EUI-48™
NODE ADDRESS
Factory-Programmed Write
Protection
Array
Data
—
X
5
X
—
4
BP1
Write-Protected
EUI-48™ Block
3
0
MEMORY ORGANIZATION
EUI-48 NODE ADDRESS PHYSICAL MEMORY MAP EXAMPLE
EEPROM
Standard
FAh
00h
24-bit Organizationally
BP0
2
1
Unique Identifier
00h
C0h
FFh
04h
WEL
—
1
WIP
—
0
A3h
12h
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
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.
24-bit Extension
EUI-64™ Support
Identifier
34h
25AA02E48
FFh
56h
DS22123B-page 13
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