Packet Structure; Start Of Packet; Address; C.4 Packet Structure - Comtech EF Data CDM-Qx Installation And Operation Manual

CDM-Qx Satellite Modem
Remote Control
C.4

Packet Structure

Controller-to-target:
Target

Start of Packet

Address

<
ASCII code 60 (4 characters)
(1 character)
Example:
Target-to-controller:
Target
Start of Packet
Address
>
ASCII (4 characters)
code 62
(1 character)
Example:
Explanations for each of the components of the packet follow.
C.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.
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.
C.4.2 Address
Up to 9999 devices can be uniquely addressed. The RS-485 base address is set by the
front panel; the RS-232 base address is always zero. Each plug-in slot (as viewed from
the back of the chassis) has its own address.
Slot
Upper Left
Lower Left
Upper Right
Lower Right
Address Instruction
De-limiter Code
/
ASCII code 47 (3 characters)
(1 character)
<0135/TRQ=70.2345{CR}
Address Instruction
De-limiter Code
/
ASCII (3 characters)
code 47
(1 character)
>0654/RSW=32{CR} {LF}
Address
Base
Base + 1
Base + 2
Base + 3
C-3
Optional
Code Qualifier
Arguments
= or ?
ASCII code 61 or 63 (n characters)
(1 character)
Optional
Code Qualifier
Arguments
=,?,!,*,# or -
ASCII code 61, (From 0 to n
63,33,42,35, characters)
126
(1 character)
Revision 6
MN/CDMQx.IOM
End of Packet
Carriage Return
ASCII code 13
(1 character)
End of Packet
Carriage Return,
Line Feed
ASCII code 13,10
(2 characters)