Comtech EF Data CDM-700 - Manual (Page 153)

CDM-700 High Speed Satellite Modem Revision 5
Remote Control MN/CDM700.IOM
11–3
11.5 Packet Structure
Controller-to-target:
Start of Packet Target Address
Address
De-limiter
Instruction
Code
Code
Qualifier
Optional
Arguments
End of Packet
<
ASCII code 60
(1 character) (4 characters)
/
ASCII code 47
(1 character) (3 characters)
= or ?
ASCII code 61
or 63
(1 character) (n characters)
Carriage Return
ASCII code 13
(1 character)
Example: <0135/TFQ=0070.2345{CR}
Target-to-controller:
Start of Packet
Target
Address
Address
De-limiter
Instruction
Code
Code Qualifier
Optional
Arguments
End of Packet
>
ASCII
code 62
(1 character) (4 characters)
/
ASCII
code 47
(1 character) (3 characters)
=, ?, !, or *
ASCII code 61,
63, 33 or 42
(1 character)
(From 0 to n
characters)
Carriage Return,
Line Feed
ASCII code 13,10
(2 characters)
Example: >0654/RSW=32{CR}{LF}
Each of the components of the packet is now explained in the following sections.
11.5.1 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.
11.5.2 Address
Up to 9999 devices can be uniquely addressed. In RS-232 applications this value is set to 0. In
RS-485 applications, the permissible range of values is 1 to 9999. It is programmed into a target
unit using the front panel keypad.
IMPORTANT
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 have its
own address.