Comtech EF Data LPOD - B.2.4 Packet Structure

LPOD C- / Ku-Band Outdoor Amplifier/ Block Up Converter (BUC) Revision 3
Appendix B MN-LPOD
B–4
B.2.3 Basic Protocol
Whether in RS-232 or RS-485 mode, all data is transmitted as asynchronous serial characters,
suitable for transmission and reception by a UART. The character format should be 8N1 (8 data
bits, no parity, 1 stop bit). The baud rate may vary between 2400 and 38400 baud.
All data is transmitted in framed packets. The Controller is assumed to be a PC or ASCII dumb
terminal, which is in charge of the process of monitor and control. The Controller is the only
device that is permitted to initiate, at will, the transmission of data. Targets are only permitted to
transmit when they have been specifically instructed to do so by the Controller.
All bytes within a packet are printable ASCII characters, less than ASCII code 127. In this
context, the Carriage Return and Line Feed characters are considered printable.
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 RS-485 mode.
B.2.4 Packet Structure
Controller-to-Target
Start of
Packet
Target
Address
Address
Delimiter
Instruction
Code
Code
Qualifier
Optional
Arguments
End of
Packet
<
ASCII code 60
(1 character)
0-9
ASCII codes
48-57
(4 characters)
/
ASCII code 47
(1 character)
A-Z, a-z
ASCII codes
65-90, 97-122
(3 characters)
= or ?
ASCII codes
61 or 63
(1 character)
(n characters)
Carriage Return
ASCII code 13
(1 character)
Example: <0412/MUT=1{CR}
Target-to-Controller
Start of
Packet
Target
Address
Address
Delimiter
Instruction
Code
Code
Qualifier
Optional
Arguments
End of
Packet
>
ASCII code 62
(1 character)
0-9
ASCII codes
48-57
(4 characters)
/
ASCII code 47
(1 character)
A-Z, a-z
ASCII codes
65-90, 97-122
(3 characters)
=, ?, !, or *
ASCII codes
61,63,33 or 42
(1 character)
(From 0 to n
characters)
Carriage Return,
Line Feed
ASCII codes
13,10
(2 characters)
Example: >0412/MUT=1{CR}{LF}
B.2.4.1 Start of Packet
¾ Controller-to-Target: This is the character '<' (ASCII code 60).
¾ 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.