Vital Product Data (VPD) Introduction
http://www.motorola.com/computer/literature B-15
B
Serial Presence Detect (SPD) Checksum Calculation
The checksum field (Byte 63) designates th e checksum for checking data
integrity (similar to parity) for bytes 0-62. It is written during board
production and can be used to verify the data integrity for these bytes.
The process for calculating the Checksum includes the following:
1. Convert the binary information in byte locations 0-62 to decimal.
2. Add together (sum) all decimal values for addresses 0-62.
3. Divide the sum by 256.
4. Convert the remainder to binary (will be less than 256).
5. Store the result (single byte) in address 63 as “Checksum.”
Note The same result can be obtained by adding the binary values in
addresses 0-62 and eliminating all but the low order byte. The
low order byte is the “Checksum.”