Pioneer PE6000 Series User Manual page 200

Appendix B
Function code L
Function code amount H
Function code amount L
Data H
Data L
CRC CHK
CRC CHK
END
CRC verity method:
CRC (Cyclical Redundancy Check) uses the format of RTU frame. The message includes error
test domain based on CRC method. CRC domain has tested all the messages. CRC domain is
two-byte and includes a binary system with 16 bits. It can add to the message after the calculation
of transmission device. The receive device can recalculate the CRC which receives messages and
compare it with the CRC domain value. If these two values are not the same, it shows transmission
error.
CRC deposits 0×FFFF first and deals with continuous 8 bytes in message and the value in
current register through a process. Only 8 bits in each byte is valid to CRC, the start bit, end bit,
and odd-even verify bit are invalid.
When CRC is added to messages, the simple function of CRC is as below:
unsigned int crc_chk_value (unsigned char *data_value, unsigned char length)
{
unsigned int crc_value = 0xFFFF;
int i;
while (length--)
{
crc_value^=*data_value++;
for (i=0; i<8; i++)
{
see definition of address.
When sending it, high byte is forward and low byte is behind.
Function code amount read by this frame. 1 means it can
read 1 function code. When sending it, high byte is forward
and low byte is behind.
Only 1 function code can be revised each time according to
this proposal.
Data answered or to be written. When sending it, high byte is
forward and low byte is behind.
Test value: CRC 16 verify value. When sending it, high byte
is forward and low byte is behind.
Calculation method see instruction of CRC verify
When it is 3.5 byte
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PE6000 User Manual