Rockwell Automation 2755-DM9, -DM9E High Speed Decoder - Manual (Page 154)

A–B
F Appendix
F–1
Transmission Check
The decoder can generate three types of transmission checks:
•
Longitudinal Redundancy Check - A byte developed by an exclusive OR
on all bytes in a message.
•
Checksum, Most Significant Byte First - Sixteen bit sum of all the bytes
in a message with the most significant byte transmitted first.
•
Checksum, Least Significant Byte First - Sixteen bit sum of all the bytes
in a message with the least significant byte transmitted first.
To assist you in understanding how transmission checks are generated, we
have provided the following example:
Assume that the message contains the following data:
Start Character = *
Label Delimiter = ¤
End of Message = CR LF
Label Data = ABC
The message would be transmitted in the following sequence:
* ¤ A B C ¤ ¤ CR LF TRANSMISSION CHECK
Note: Refer to Figure 6.5 and Table 6.A for data transmission format.
The table on the following page shows what the transmission checks would
be for the above message.