Honeywell CD3000M-2PH User Manual page 37

Honeywell
9.2.3 C Language CRC 16 Example
static short CRC16 (unsigned char *p_first,unsigned char *p_last)
{
unsigned int crc=0xffff;
short j;
for (;p_first<=p_last;p_first++)
{
crc ^= *p_first;
for(j=8;j>0;j--)
{
if(crc & 0x0001)
else
}
}
return (crc);
}
9.2.4 Read Holding Registers (Read n Words) – Function 03
The message sent to the Controller to obtain the value of one or more registers comprises the
following eight bytes:
Addr. unit Func.
3
3Hex
The normal reply will echo the first two characters of the message received followed by a single-
byte data byte count (which will not include itself or the CRC).
For this message, the count value equals the number of parameter values read multiplied by two.
Following the byte count, the specified number of parameter values are transmitted, followed by
the CRC16 bytes:
Addr. unit Func.
3
3Hex
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CD3000M-2PH from 125A to 700A
{
crc = crc >> 1;
crc ^= 0xA001;
}
{
crc = crc >> 1;
}
Address
1° word
HI LO
Cont. 1° Value
HI
N° of Word
HI LO
Last Value
LO HI
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User's Manual
CRC 16
HI LO
CRC 16
LO HI LO