Packet Structure; Start Of Packet; Address - Comtech EF Data CDM-550T Manual

CDM-550T Satellite Modem
15.5

Packet Structure

Controller-to-target:

Start of Packet

Target Address
<
ASCII code 60
(1 character) (4 characters)
Example:
Target-to-controller:
Start of Packet Target

Address

>
ASCII
code 62
(1 character) (4 characters)
Example:
Each of the components of the packet is now explained.
15.5.1 Start Of Packet
Controller to Target: This is the character '<' (ASCII code 61)
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.
15.5.2 Address
Up to 9,999 devices can be uniquely addressed. In EIA-232 applications this value is set
to 0. In EIA-485 applications, the permissible range of values is 1 to 9999. It is
programmed into a target unit using the front panel keypad.
Important note: 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.
Rev. 1.3
Address Instruction
De-limiter Code
/
ASCII code 47
(1 character) (3 characters)
<0135/TFQ=70.2345{CR}
Address Instruction
De-limiter Code
/
ASCII
code 47
(1 character) (3 characters)
>0654/RSW=32{CR}{LF}
Code Optional
Qualifier Arguments
= or ?
ASCII code 61
or 63
(1 character) (n characters)
Code Qualifier Optional
Arguments
=, ?, !, or *
ASCII code 61,
63, 33 or 42 (From 0 to n
(1 character) characters)
Remote Control
End of Packet
Carriage Return
ASCII code 13
(1 character)
End of Packet
Carriage Return,
Line Feed
ASCII code 13,10
(2 characters)
15–3