Communicating With The Plc; Uss Communication - Siemens SINAMICS V20 Series Operating Instructions Manual

Communicating with the PLC

The SINAMICS V20 supports communication with Siemens PLCs over USS on RS485. You
can parameterize whether the RS485 interface shall apply USS or MODBUS RTU protocol.
USS is the default bus setting. A screened twisted pair cable is recommended for the RS485
communication.
Make sure that you terminate the bus correctly by fitting a 120 R bus termination resistor
between the bus terminals (P+, N-) of the device at one end of the bus and a termination
network between the bus terminals of the device at the other end of the bus. The termination
network should be a 1.5 k resistor from 10 V to P+, 120 R from P+ to N- and 470 R from N-
to 0 V. A suitable termination network is available from your Siemens dealer.
0 V
6.1

USS communication

Overview
One PLC (master) can connect a maximum of 31 inverters (slaves) through the serial link
and control them with the USS serial bus protocol. A slave can never transmit without first
being initiated by the master so that direct information transfer between individual slaves is
not possible.
Data exchanging:
SINAMICS V20 Inverter
Operating Instructions, 07/2012, A5E03728167
0 V P + N - 0 V P + N -
6
10 V P + N - 0 V
105