Interface USB/RS232/RS485 eng (24.11.2014)
- 4 -
Kompetent für Elektroniksysteme
Interface USB/RS232/RS485 eng (24.11.2014)
- 5 -
Kompetent für Elektroniksysteme
RS485 is a differential 2-wire (+GND) data interface for 2 or more participants. The maximum length
is about 1000m. Both ends of the bus need to be terminated with 120 Ohm, branches should be
short and should not include a terminating resistor.
The RS485 is already equipped with the suitable terminating resistors. For few and short connection
lines, these can remain in place. In other cases or if connection problems are encountered the surplus
resistors need to be removed (R14-R16). Another possibility to improve the connection is to reduce
the rate of the data transfer.
Ex factory, the RS485 is part of the "Line" connector and, thus, transferred in the same cable as the
AF lines. Hence, only one cable is necessary to connect 2 interfaces. Depending on the used cables,
the cable length and the number of interfaces, coupling of the data telegrams with the AF lines might
occur. In this case, the RS485 sockets can be connected using a separate cable. To disconnect the
RS485 lines of "Line" socket, open JP1 and JP2.
RS485 Interface
The LEDs at the socket "Radio/Major" (green on the right and yellow on the left) display the
different statusses of operation:
- left LED shortly flashes once per second: interface is trying to establish a connection to the Major
or the radio
- right LED is on: connection to the Major established
- left LED is on: connection to the radio established
If a connection is eestablished, the LEDs are flashing for a short time on receiving a telegram. The
left LED flashes for telegrams from the radio, the right LED flashes for telegrams from the Major.
LEDs
The interface has 2 AF inputs and outputs. The input and output at the socket "Radio/Major" is
single-ended (one pin is GND), while the input and output of the socket "Line" is potential-free.
Amplification is possible in both directions from -20dB to +10dB and can be adjusted using the
service interface.
AF Connection
