Comtech EF Data SNM-1000 - Manual (Page 150)

SNM-1000 Node Control Modem Revision 3
Remote Control Operation MN/SNM1000.IOM
A–2
A.2 Abnormal Condition Responses
If a satellite modem receives a message which does not match the established protocol or
cannot be implemented, a negative acknowledgment message is sent in response. The
possible message formats are:
• <channel_no> ?ER1_PARITY ERROR'cr''lf']
(Error message for received parity errors.)
• <channel_no> ?ER2_INVALID PARAMETER'cr''lf']
(Error message for a recognized command which cannot be implemented or has parameters
which are out-of-range.)
• <channel_no> ?ER3_UNRECOGNIZABLE COMMAND'cr''lf']
(Error message for unrecognizable command or bad command syntax.)
• <channel_no> ?ER4_MODEM IN LOCAL MODE'cr''lf']
(Modem in local error, use the REM command to go to remote mode.)
• <channel_no> ?ER5_HARD CODED PARAMETER'cr''lf']
(Error message indicating that the parameter is hardware dependent and may not be changed
remotely.)
A.2.1 Character Set
The interface responds to ASCII characters in the range of 0x00 to 0x7F. The 8th bit
(most significant) is not generated on the transmit side and is ignored on the receive side.
A.2.2 Status Lines and Flow Control
The interface ignores all status inputs.
A.2.3 Message Structure
A message is either a command or a response. Each message is made up of three
elements:
• Prefix
• Message body
End character