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Technical Manual 1.02, C350 Professional
RS485 communication ports (EIA/TIA-485-A compatible)
RS485 is a multi-drop network with a maximum of 32 units connected simultaneously to
the bus. The RS485 bus contains a RS485+ (non-inverting) and a RS485- (inverting)
signal, as well as a signal ground, which must always be connected to the common signal
ground for all units connected to the RS485 bus!
The maximum cable length for the RS485 bus is according to EIA/TIA-485-A standard
(max. 1200m @ <100kbit); this limit is highly influenced by the quality of the cable,
signaling rate, noise etc.
At longer cable lengths, noisy environments or high communication speed it might be
necessary to terminate the transmission line with a 120
transmission line to terminate it and avoid signal reflections. If the C350 pro is use as
endpoint unit the hardware jumper JP7 (standard port) / JP12 (optional port) can be
installed to terminate the RS485 communication lines with 120 ohm.
Both the standard and the optional RS485 port can be used as general-purpose RS485
serial port or as IO extension module(s) port. When used with supported MODBUS IO
extension modules, general purpose use is disabled. The RS485 port signals are available
on the pluggable screw terminals.
Further details on the MODBUS IO extension modules and use are available in the M2M
Control IDE on-line help.
By default the RS485 communication lines are not terminated with 120 ohm. For
placement and configuration of the hardware jumpers inside the unit, please refer to the
configuration guide in Appendix A.
RS485 port (standard)
This port is always available on the C350 pro unit and is not shared with other resources.
Standard RS485 port pins.
Pin
Name
9
SGND
10
RS485_1+
11
RS485_1-
12
SGND
1
Assuming use of a CAT5 twisted pair cable
M 2 M C o n t r o l
by Infranet Technologies GmbH
Tempowerkring 2
21079 Hamburg
Germany
Description
Signal ground
RS485 non-inverting signal for standard RS485 port
RS485 inverting signal for standard RS485 port
Signal ground
1
ohm resistor at each end of the
Ph: +49.40.69647-260
Fax: +49.40.69647-259
Email:
info@m2mcontrol.de
Web: www.m2mcontrol.de
Page 18 of 38
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