Hardware Manual PCD1.M2110R1 │ Document 27-619 │ Version ENG 04 │ 2018-08-20
Saia-Burgess Controls AG
Communications Interfaces
6
6-4
On-board │ Port#0 RS-485
6.1.3
Port #0 (RS-485,
not electrically isolated)
In S-Bus, Modbus or MC4 communications mode, an RS-485 link can be
established via port 0 with terminal block X3, terminals 38 and 39
39
D
/D
WD
WD
RX - TX
/RX - /TX
S1
38
37
36
35
34
33
32
31
30
RS-485
Bus cable
X3
O
C
X3
S1
Switch S1, connecting or disconnecting the RS-485 termination resistors
With switch S1, the terminating resistors are switched on or off. Switch S1 must
be set to “C” (closed) at both outer stations. For all other stations switch S1
remains in the position “O” (factory setting).
Schematic diagram of an RS-485 bus with terminating resistors.
+5 V
/RX - /TX
n
n
39
n
/n
/n
/n
38
RX - TX
+5 V
Pull up
330 Ohm
Termination
Resistor
150 Ohm
Segment length max. 1200 m
max. 32 stations
Bus RS-485
First station
Middle stations
End station
Pull down
330 Ohm
For more details see in the Manual 26-740, Installation components for RS-485
Networks.
