Programming Guide

CHUMP Reference Guide
10
Message Tail
The message tail contains a type indicator (; or !), an optional 8-
bit Frame Checksum (FCS), and an end-of-packet indicator
(CR and/or LF). The format is as follows:
;<FCS><CR and/or LF> for message tails with a checksum
!<CR and/or LF> for message tails without a checksum
The FCS is expressed as two ASCII bytes and is a sum of the
bytes of the rest of the message. The FCS starts at the first
character, “}” or “{“, and ends at the semicolon FCS delimiter
“;”. Many of the shorter commands explained in the Command
Description section include FCS values (refer to the Ro
command).
NOTE: The FCS can be eliminated for debug purposes by using
the “!” message tail. However, installed systems should
always use the FCS.
Refer to Appendix B for sample checksum calculation code.