21.4.11
UNIGATE fieldbus gateway for Fast Ethernet V. 2.1
25
Deutschmann Automation GmbH & Co. KG
Hardware ports, switches and LEDs
8.5.3
Slide switch (RS485/RS422 termination)
If the gateway is operated as the first or last physical device in the RS485 bus, there must be a
bus termination at this gateway. In order to do this, either a bus terminating resistor in the con-
nector or the resistor (150
) integrated in the gateway must be activated. In order to do this,
slide the slide switch to position ON. In all other cases, the slide switch must remain in position
OFF. Please refer to the general RS485 literature for further information on the subject of bus ter-
minations.
If the integrated resistor is used, please allow for the fact that this also activates a pull-down
resistor (390
) to ground and a pull-up resistor (390
) to VCC.
At the RS422-interface the transmission line is terminated. The receive line is always firmly ter-
minated.
