RTCU MX2 turbo Technical Manual V2.04
Logic IO ApS.
Ph: (+45) 7625 0210
Holmboes Allé 14
Fax: (+45) 7625 0211
8700 Horsens
Page 15 of 36
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Denmark
www.logicio.com
RS485
RS485 is available on the X2 connector as serial port 1. The RS485 bus a multi-drop network with a
maximum of 32 units connected simultaneously to the bus. The RS485 bus contains an RS485+
(
non-inverting
) and an 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
1
ohm resistor between terminal RS485+ and terminal
RS485- at each end of the wires to avoid signal reflections etc.
X2: 12 pin COM connector overview
Pin
Name
Description
5
RS485+
RS485 non-inverting signal (A)
6
RS485-
RS485 inverting signal (B)
11
SGND
Signal Ground
1 Assuming use of a CAT5 twisted pair cable
