Packet Structure; Start Of Packet; Target Address; Address Delimiter - Comtech EF Data CDM-740 Installation And Operation Manual

CDM-740 Advanced Satellite Modem
Remote Control
A.4

Packet Structure

Start of Target
Packet Address
<
ASCII code
60
(1 character) (4 characters)
Example: <0000/RSH=30[cr]
Start of Target
Packet Address
>
ASCII code
62
(1 character) (4 characters)
Example: >0000/BBU=107[cr][lf]
A.4.1

Start of Packet

Controller-to-Target: This is the character '<' (ASCII code 60).
Target-to-Controller: This is the character '>' (ASCII code 62).
Because this is used to provide a reliable indication of the start of packet, these two characters
may not appear anywhere else within the body of the message.
A.4.2

Target Address

Up to 9,999 devices can be uniquely addressed. In EIA-232 applications this value is set to 0.
The Controller sends a packet with the address of a Target – the destination of
the packet. When the Target responds, the address used is the same address,
to indicate to the Controller the source of the packet. The Controller does not
IMPORTANT
have its own address.
A.4.3

Address Delimiter

This is the character '/' (forward slash) (ASCII code 47).
A.4.4

Instruction Code

This is a three-character alphabetic sequence that identifies the subject of the message. Wherever
possible, the instruction codes have been chosen to have some significance. For Example: TFQ
for Tx FreQuency; RMD for Rx MoDulation type, etc. This aids in the readability of the
Controller-to-Target
Address De- Instruction
limiter Code
/
ASCII code
47
(1 character) (3 characters)
Target-to-Controller
Address De- Instruction
limiter Code
/
ASCII code
47
(1 character) (3 characters)
A–2
Code Optional
Qualifier Arguments
= or ?
ASCII codes
61 or 63
(1 character) (n characters)
Code Optional
Qualifier Arguments
=, ?, !, or *
ASCII codes
61,63,33 or
42
(From 0 to n
(1 character) characters)
Revision 0
MN-CDM740
End of Packet
Carriage Return
ASCII code 13
(1 character)
End of Packet
Carriage Return,
Line Feed
ASCII codes
13,10
(2 characters)