Message Structure; Start Character; A.2 Message Structure; A.2.1 Start Character - Comtech EF Data SDM-100A Installation And Operation Manual

Remote Control Operation

A.2 Message Structure

The ASCII character format used requires 11 bits/character:
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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.
The general message structure is as follows:
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A.2.1 Start Character

A single character precedes all messages transmitted on the remote link. This character flags the start of a
message. This character is:
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A.2.2 Device Address

The device address is the address of the one satellite modem which is designated to receive a transmitted
command, or which is responding to a command.
Valid device addresses are 1 to 3 characters long, and in the range of 1 to 255. Address 0 is reserved as a
global address which simultaneously addresses all devices on a given communications link. Devices do not
acknowledge global commands.
Each satellite modem which is connected to a common remote communications link must be assigned its
own unique address. Addresses are software selectable at the modem, and must be in the range of 1 to 255.
A–2
1 start bit
7 information bits
1 parity bit
2 stop bits

Start Character

Device Address
Command/Response
End of Message Character
"<"
for commands
">"
for responses
SDM-100A Satellite Modem
Rev. 0