Packet Structure - Comtech EF Data CDM-570A Installation And Operation Manual

CDM-570A/570AL Satellite Modem with Optional Packet Processor
Serial-based Remote Product Management
All messages from Controller-to-Target require a response, with one exception: 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. The exception to
this is when the Controller broadcasts a message (such as Set Time/Date) using Address 0, when the Target is set to EIA-485 mode.
8.2.2

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.
Start of Packet
<
ASCII code 60
(1 character)
Packet "issued command" example:
Packet "issued query" example:
Start of Packet
>
ASCII code 62
(1 character)
Packet example – response received for issued query: >0000/RSW=32[cr][lf]
Detailed description of the packet components follow.
Target Address Address Delimiter
/
ASCII code 47
(4 characters) (1 character)
<0000/RSW=32[cr]
<0000/RSW?[cr]
Target Address Address Delimiter
/
ASCII code 47
(4 characters) (1 character)
Controller-to-Target
Instruction Code Code Qualifier
= or ?
ASCII codes 61 or 63
(3 characters) (1 character)
Target-to-Controller
Instruction Code Code Qualifier
=, ?, !, or *
ASCII codes
61, 63, 33, or 42
(3 characters) (1 character)
8–3
MN-CDM570A
Revision 3
Optional Arguments End of Packet
Carriage Return
ASCII code 13
(n characters) (1 character)
Optional Arguments End of Packet
Carriage Return, Line
Feed
ASCII codes 13,10
(From 0 to n characters) (2 characters)