Comtech EF Data SDM-300A - Manual (Page 3)

Filename: T_ERRATA
1
Errata A
Comtech EF Data Documentation Update
Subject: Appendix A. Remote Control Operation
Date: June 21, 2005
Document: SDM-300A Satellite Data Modem Installation and Operation
Manual, Rev. 4, dated June 15, 2000
Part Number: MN/SDM300A.EA6
Collating Instructions: Attach this page to page A-1
Comments:
Change paragraphs A. 1and A.2 are highlighted to read:
Change Specifics:
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'
• Address De-limiter ‘/’
• Command/Response
• Qualifier ‘_’
• Optional Arguments ‘n, m, x, y, z’
• End of Message Character