Comtech EF Data SNM-1001 - Manual (Page 62)

SNM-1001 Network Control Modem Remote Control Operation
Rev. 1 A–3
A.2 Message Structure
The ASCII character format used requires 11 bits/character:
•
1 start bit
•
7 information bits
•
1 parity bit
•
2 stop bits
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:
•
Start Character
•
Device Address
•
Command/Response
•
End of Message Character
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:
•
“<” for commands
•
“>” for responses
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.