RMV Operations Manual Revision Copyright illunis LLC, 2014
Page 134
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FAQ# 24
:
Checksum Calculation
The checksum is used in two different implementations; data only (default) and command and
data. Consider the command packet: {wCCIIDDDDSS} where CC = command, II = Index, DDDD = da-
ta, and SS = checksum. For the data only we use a C function as follows;
UINT8 CheckSum( UINT16 twobytes )
{
UINT8 checksum,byte0,byte1;
byte0 = twobytes & 0x00ff;
byte1 = (twobytes >> 8) & 0x00ff;
checksum = byte0 + byte1;
checksum = 256 - checksum;
return
(checksum);
}
The checksum for the data only is:
SS = CheckSum( DDDD );
For the checksum of the command and data we use:
SS = CheckSum( DDDD ) + CheckSum( CCII );
Where DDDD is 4 digit hex. and CCII is a concatenated 4 digit hex number.
FAQ# 25
:
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