PD-113-57/60-SE / TMCM-113-60-SE Hardware Manual (V1.52 / 2011-DEC-06)
14
BUS TERMINATION: Especially for longer busses and/or multiple nodes connected to the bus and/or high
communication speeds, the bus should be properly terminated at both ends. The PD-113-57/60-SE-485 integrates
a 120 Ohm termination resistor that can be placed between both RS485 bus wires by setting a jumper.
Figure 4.8: Jumper for placing bus termination
NUMBER OF NODES: The RS485 electrical interface standard (EIA-485) allows up to 32 nodes to be connected to
a single bus. The bus transceiver used for the PD-113-57/60-SE-485 units (SN65HVD3082ED) has just 1/8 of the
standard bus load and allows a maximum of 256 units to be connected to a single RS485 bus.
NO FLOATING BUS LINES: Avoid floating bus lines while neither the host/master nor one of the slaves along the
bus line is transmitting data (all bus nodes switched to receive mode). Floating bus lines may lead to
communication errors. In order to ensure valid signals on the bus it is recommended to use a resistor network
connecting both bus lines to well defined logic levels. In contrast to the termination resistors this network is
normally required just once for a bus. Certain RS485 interface converters available for a PC already include these
additional resistors (e.g. USB-2-485 [USB-2-485]).
Slave
Slave
+5V
node node
n-1
n
pull-up (1k)
RS485+ / RS485A
RS485- / RS485B
termination resistor
120 Ohm
pull-down (1k)
GND
Figure 4.9: Resistor network to avoid floating bus lines
Copyright © 2011, TRINAMIC Motion Control GmbH & Co. KG
TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
