Checksums

The PIROM includes multiple checksums. Table: Byte ROM Checksum Values includes the checksum values for each section defined in the 128-byte ROM.

Checksums are automatically calculated and programmed by Intel. The first step in calculating the checksum is to add each byte from the field to the next subsequent byte. This result is then negated to provide the checksum.

Example: For a byte string of AA445Ch, the resulting checksum will be B6h.

• • AA = 10101010 44 = 01000100 5C = 01011100
  • AA + 44 + 5C = 01001010

Negate the sum: 10110101 +1 = 10110110 (B6h)