SIMOREG 6RA70 Siemens DC Master Variable Speed DC Drive
Design & Mode of Operation –
Serial Interface

Design and Mode of Operation6RA70 DC Master

Serial interfaces

The following serial interfaces are available:

  • One serial interface on connector X300 on the PMU for a USS protocol to the RS232 or RS485 standard. For connection of optional OP1 S operator panel or for PC-based DriveMonitor.
  • One serial interface at terminals of basic electronics board, two-wire or four-wire RS485 for USS protocol or peer-to-peer connection.
  • One serial interface at terminals of terminal expansion board (option), two-wire or four-wire RS485 for USS protocolor peer-to-peer connection.
  • PROFIBUS DP on a supple mentary card (optional).
  • SIMOLINK on a supplementary card (optional) with fiber optic connection.
  • CAN protocol (Controller Area Network) on a supplementary card (optional).
  • CBD protocol (Communication Board DeviceNet) on a supplementary card (optional).

Physical characteristics of interfaces

  • RS232: +12 V interface for point-to-point connection.
  • RS485: 5 V normal mode interface, noise-proof, for an additional bus connection with a maximum of 31 bus nodes.

USSTM protocol

Disclosed SIEMENS protocol, easy to program on external systems, e.g. on PC, any master interfaces can be used. The drives operate as slaves on a master. Drives are selected via a slave number.

The following data can be exchanged via the USS protocol:

  • PKW data for writing and read ing parameters.
  • PZD data (process data) such as control words, setpoints, status words, actual values.

Connector numbers are entered in parameters to select the transmit data (actual values), the receive data (setpoints) represent connector numbers that can be programmed to act at any intervention points.

Peer-to-peer protocol 

The peer-to-peer protocol is used to link one converter to another. With this mode, data are exchanged between converters, e.g. to build a setpoint cascade, via a serial interface. Since a serial interface is employed as a four-wire line, it is possible to receive data from the upstream converter, condition them (e.g. through multiplicative weighting) and then send them to the downstream converter. Only one serial interface is used for the whole operation.

The following data can be exchanged between converters:

  • Transmission of control words and actual values.
  • Reception of status words and setpoints.

Up to five data words are transmitted in each direction. Data are exchanged on the basis of connector numbers and intervention points.

The serial interfaces can be operated simultaneously. For example, the first interface can be used as an automation link (USS protocol) for open-loop control, diagnostics and specification of the master setpoint. A second interface operates in conjunction with the peer-to-peer protocol to act as a setpoint cascade.


To purchase drives and/or parts, contact us at:
Phone (815) 725-9696,
Toll Free (866) 492-9888,
Fax (815) 725-9393 or


Siemens Energy & Automation
SIMOREG DC Master Base Drive Operating Instructions