Motorola MVME2400 Series Programmer's Reference Manual page 48

Board Description and Memory Maps
1
The VPD consists of a header section, followed by contiguous formatted
data packets. The header section consists of eye-catcher and size fields,
and the data packets consist of identifier, data length, and data content
fields.
The header section begins with an eye-catcher field that can be used to
verify the existence of an initialized VPD SROM (an optional EEPROM
CRC packet may also be used to verify the integrity of the VPD content).
The "size" field contains the total number of bytes assigned to the VPD
portion of the SROM.
Each packet begins with a unique identifier field that defines the content
and data structure of the packet's data section. The data length field
contains the size of the data section in bytes. This is also added to the data
section base address to locate the starting address of the following VPD
packet. Different data section lengths are sometimes used to denote
different revision levels or array sizes for packets of a particular identifier.
Packets must be contiguous but may be placed in any order. The
termination packet identifier marks the end of the VPD and must
immediately follow the last valid packet. Common VPD packets include
assigned ethernet address, board serial number, processor internal/external
clock frequency, processor identifier, connector population, and other
packets.
Customers may add additional data packets which are assigned to the user
range of packet identifiers and adhere to this specification. Although the
addition of user packets is discouraged, one potential user packet
application is the specification of customer installed hardware modules.
Additional information on VPD Data Definitions, Product Configuration
Options, FLASH Memory Configuration Data, L2 Cache Configuration
Data, and an Example of VPD SROM data can be found in
MVME2400 VPD Reference
1-24
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Appendix A,