Datasheet

 2012-2018 Microchip Technology Inc. DS20002300C-page 44
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 (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).
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 to 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