Comtech EF Data CDM-800 - Manual (Page 111)

CDM-800 Gateway Router Revision 1
Serial-based Remote Product Management MN-CDM800
6–3
When the user‐supplied terminal emulator program is configured correctly, upon power‐up of the CDM‐800, the CLI Info Screen
appears, followed by the CLI command prompt CDM‐800>. From here, type “help[cr]” or “?[cr]” (without the quotes) to display the
CDM‐800 available commands and queries, and to review instructions for using the interface.
6.2 Remote Commands and Queries Overview
6.2.1 Basic Protocol
In an EIA‐232 configuration, the Controller device is connected directly to the Target device via a two wire‐plus‐ground connection. All data
is transmitted in framed packets as asynchronous serial characters, suitable for transmission and reception to the Controller using a
universal asynchronous receiver/transmitter (UART). Controller‐to‐Target data is carried via EIA‐232 electrical levels on one conductor, and
Target‐to‐Controller data is carried in the other direction on the other conductor:
• Controller‐to‐Target: The Controller device (e.g., the user PC/CLI) is used to transmit instructions (commands) to – or to request
information from (queries) – the Target device (i.e., the CDM‐800).
• Target‐to‐Controller: The Target, in return, only transmits response information to the Controller when specifically directed by
the Controller.
For Serial Remote Control, all issued commands (Controller‐to‐Target) require a response (Target‐to‐Controller). This response is either
to return data that has been queried by the Controller, or to confirm the Target’s receipt of a command to change the Target’s
configuration.
6.2.2 Packet Structure
The exchange of information is transmitted, Controller‐to‐Target and Target‐to‐Controller, in packets. Each packet contains a finite
number of bytes consisting of printable ASCII characters, excluding ASCII code 127 (DELETE).
In this context, the Carriage Return and Line Feed characters are considered printable. With one exception, all messages from Controller‐
to‐Target require a response – this will be either to return data that has been requested by the Controller, or to acknowledge reception of an
instruction to change the configuration of the Target.