Comtech EF Data LPODnet - Manual (Page 35)

LPODnet M&C Netbook Accessory Revision 3
Ethernet-Based M&C using the LPODnet MN-LPODNET
3–5
3.5.1 Basic Remote Control Protocol via the Telnet Interface
Whether in EIA-232 or EIA-485 mode, all remote control 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 that is in charge of the process of
monitor and control when using the LPODnet is assumed to be the Telnet Client interface. 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 EIA-485 mode.
3.5.1.1 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}
3.5.1.1.1 Start of Packet
 Controller-to-Target: This is the less-than character '<' (ASCII code 60).
 Target-to-Controller: This is the greater-than character '>' (ASCII code 62).