Serial Presence Detect Checksum Calculation - SMART Embedded Computing MVME7100ET Programmer's Reference Manual

crcValueFlipped <<= 1;
dataBitValue = crcValue & 1;
crcValue >>= 1;
crcValueFlipped += dataBitValue;
}
crcValue = crcValueFlipped ^ 0xffffffff;
return (crcValue);
}
A.9.2

Serial Presence Detect Checksum Calculation

The calculation process is as follows:
1. Convert binary information, in byte locations 0 - 62, to decimal.
2. Add together (sum) all decimal values for addresses 0 - 62.
3. Divide sum by 256.
4. Convert remainder to binary (will be less than 256).
5. Store result (single byte) in address 63 as "Checksum".
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".
Table A-3
SPD Byte Address
00 (0x00)
01 (0x01)
02 (0x02)
03 (0x03)
:
:
60 (0x3C)
61 (0x3D)
62 (0x3E)
Decimal Total
MVME7100ET Single Board Computer Programmer's Reference (6806800K88C)
Checksum Calculation Example
Serial PD
0010 0100
1111 1110
0000 0000
0000 0000
:
:
0000 0000
0000 0000
0000 0000
-
Programmable Configuration Data
Convert to Decimal
> 36
> + 254
> + 0
> + 0
> + 0
>
> + 0
> + 0
> + 0
- 290
67