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5.7 Error messages
Three different kind of errors might occur:
The body is an invalid command
The checksum is not correct
The device cannot be addressed (it might be switched off…)
The information sent back to the RCM about these errors does not include the status register
Error Protocol "EP"
Description: Via this answer the RCM is told by the RCS of class m that the body has been an invalid
command.
Example: The
RCM has sent a command x to the RCS.
Message
<STX> <TYPE> <ADDRH> <ADDRL> <Body> <STATH> <STATL <CHKH> <CHKL> <ETX>
m0 2 y 48
Since the command y does not exist for an
RCS of class m, the RCS sends this message
back to the
RCM, adds the extension EP (Error Protocol), and calculates the new check-
sum.
Answer
<STX> <TYPE> <ADDRH> <ADDRL> <Body> <chksm> <ERR> <CHKH> <CHKL> <ETX>
m 0 2 y 48 EP 4 9
Error Checksum "EC"
Description: Via this answer the RCM is told by the RCS of class m that the checksum has not beeen
correct.
Example: The
RCM has sent the following command:
Message
<STX> <TYPE> <ADDRH> <ADDRL> <Body> <STATH> <STATL <CHKH> <CHKL> <ETX>
m0 2 t 30
The correct checksum of the above command is 43. The
RCS detects an checksum error,
sends the command back to the
RCM and adds the extension EC (Error Checksum)
Answer
<STX> <TYPE> <ADDRH> <ADDRL> <Body> <chksm> <ERR> <CHKH> <CHKL> <ETX>
m 0 2 t 30 EC 2 e