Message Structure; Start Character; Device Address - Comtech EF Data SNM-1001L Installation And Operation Manual

SNM-1001L Satellite Modem
Remote Control Operation
B.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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B.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:
"<"
">"
B.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.
Note: 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.
1 start bit
Information and Parity bits (select one)
7 information bits and 1 parity bit (Odd/Even) or 8 information bits (None)
2 stop bits
Start Character
Device Address
Command/Response
End of Message Character
for commands
for responses
B–2
Revision 1
MN/SNM1001L.IOM