Beside the network interface, the sat-nms LFTXRX also provides an RS232 serial port which can
be used to control the device remotely. Depending on the device address set, the LFTXRX either
runs framed protocol with start/stop characters and checksum or it provides a dumb terminal
interface. The RS232 interface operates by default at 9600 baud, no parity, 8 data bits, one stop
bit.
You can configure the
baud rate
on the front panel.
If an address 'A' .. 'G' is
selected
, the LFTXRX expects each message it receives to be packed
into a frame as described below.
char #
example
description
1
{
start character, always ' {'
2
A
device address (A..G)
3
t
first character of the message body
.
m
message body ...
.
p
..
.
0
..
.
=
..
n-1
?
last character of the message body
n .tc}
end character, always '} '
n+1
.
checksum
The checksum byte is calculated using an algorithm as implemented by the following formula:
This protocol type is known as MOD95- or Miteq protocol . The LFTXRX also packs it's reply in a
protocol frame as described above. incomplete frames, checksum errors or address mismatches
let the device ignore the message. The time between the characters of a message must be less
than 5 seconds or the device will treat the message as incomplete.
If the LFTXRX is set to the device address 'NONE', it uses a simple line protocol instead of the
framed protocol described above. Messages sent to the device have to be terminated with a
carriage return character (ASCII 13), the device terminates replies with a CR/LF pair (ASCII
13/10). There is no echo for characters entered, hence this protocol easily may be used for
computer based remote control.
The sat-nms LFTXRX contains an SNMP agent listening at UDP port 161. The SNMP agent
provides a common subset pf the MIB-II system / interface parameters and gives full access to the
remote control capabilities of the LFTXRX with a number of MIB objects placed in the
private.enterprises tree.
(C) 2021, SatService GmbH
www.satnms.com
LF20-UM-2107 Page 33/43
