Comtech EF Data SDM-300A - Manual (Page 393)

A–1
Appendix A. Remote Control
Operation
This appendix describes the remote control operation of the SDM-300A.
• Firmware number: FW/6535-1AP
• Software version: 7.1.13
Note: The firmware referenced in this manual may be an earlier version of the actual firmware
supplied with the unit.
A.1 General
Remote control and status information is transferred via a RS-485(or RS-232) serial
communications link. Commands and data are transferred on the remote control
communications link as US ASCII encoded character strings. The remote communications link
is operated in a half duplex mode. A remote controller or terminal initiates communications on
the remote link. The SDM300A never transmits data on the link unless it is commanded to do
so.
A.2 Message Structure
The ASCII character format requires 11 bits/character: 1 start bit, 7 information bits with 1
parity bit (odd/even) or 8 information bits with no parity bits, and 2 stop bits.
Messages on the remote link fall into the categories of commands and responses. Commands are
messages transmitted to a satellite modem, while responses are messages returned by a satellite
modem in response to a command.The general message structure is as follows:
• Start Character
• Device Address
'add'
• Command/Response
• End of Message Character