janitza UMG 801, User Manual

Page: 49 / 106

www.janitza.de UMG 801
49
B A C
9.3 RS-485 interface (serial interface)
The RS-485 interface of this device is designed as
a 3-pole plug contact and communicates using the
Modbus RTU protocol.
For the connection capacity of the terminals, see
chapter „19. Technical data“ on page 96.
Termination
(termination
resistance)
Connection of
additional
devices
C
Data GND
RS-485 bus
A
B
A
B
C
Functional earth
Illustration example:
RS-485 interface of the UMG 801 (in the middle of a bus topol-
ogy - 3-pole plug contact).
Data GND
RS-485 bus
A
B
C
Functional earth
B A C
Examples of RS-485 interface - UMG 801
Fig. Example:
RS-485 interface of the UMG 801 (at the beginning of a bus topol-
ogy - 3-pole plug contact).
RS-485 interface - UMG 801:
Termination
(termination
resistance)
Connection of
additional devices
INFORMATION
·The device contains an integrated termination re-
sistor (switch S1). For a UMG 801 at the beginning
or end of a bus segment, terminate the device via
the switch S1 - S1 to switch position "I" (on). See
section „9.3.2 Termination resistors/Termination“
on page 50.
·CAT cables are not suitable for bus wiring!
Recommendation:
Use Unitronic Li2YCY(TP)
2x2x0.22 (Lapp cable) for bus wiring.
·A segment of an RS-485 bus structure can contain
up to 32 nodes/devices. If there are more than 32
nodes/devices, use repeaters to connect seg-
ments.
·To prevent the addition of leakage currents when
using several devices, install the Data GND as the
functional earth (see adjacent figures)!
Upper terminal row
Upper terminal row