Comtech EF Data SDM-2020 - Manual (Page 218)

Appendix A. REMOTE CONTROL
OPERATION
This appendix describes the remote control operation of the SDM-2020 Modulator.
• Firmware number: FW/5613-1AG
FW/5613-2AG
• Software version: 9.1.2
Remote controls and status information are transferred via an EIA-485 (optional
EIA-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 modem
never transmits data on the link unless it is commanded to do so.
Some commands and status information are interface-type dependent.
A.1 M
ESSAGE
S
TRUCTURE
The ASCII character format used requires 11 bits/character:
• 1 start bit
• 1 parity bit (Not applicable to 8 information bit setup)
• 2 stop bits
• 7 information bits or 8 information bits
Messages on the remote link fall into the categories of commands and responses.
Commands are messages, which are transmitted to a satellite modem, while responses are
messages returned by a satellite modem in response to a command.
A-1