Basic Serial Protocol - Comtech EF Data CDM-710 Installation And Operation Manual

CDM-710/L Broadcast Satellite Modem
Serial Interface Operation

9.2 Basic Serial Protocol

Serial data can be transmitted and received by a Universal Asynchronous Receiver/Transmitter (UART).
Serial data is transmitted as asynchronous serial characters:
• Asynchronous character format is 8-N-1 (8 data bits, no parity, 1 stop bit)
• Baud rate can vary from 1200 through 57600 baud.
Serial data is transmitted in framed packets. All bytes within a packet are printable ASCII characters less than ASCII
code 127 (DELETE). The Carriage Return and Line Feed characters are considered printable.
The Controller device manages the monitor and control processes. It is the only device that can start data
transmission at will. Messages sent from the Controller to the Target require responses, except in these cases:
• Acknowledging receipt of a "command" – an instruction message issued by the Controller – to change the
configuration of the Target.
• Returning data that was requested by the Controller – the Target response to a "query" – that requests
information from the Target.
• When the Controller broadcasts a message using Address 0 and the Target is set to EIA-485 mode.
• Target devices can transmit data only when the Controller tells them to.
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MN/CDM710.IOM
Revision 12