Siemens Simatic S7-300 CPU 31xC Series User Manual

Commissioning
8.4 Commissioning the Modules
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
8-17
MPI addresses for service PGs
If there is no stationary PG, we recommend:
To connect a PG to an MPI subnet with "unknown" node addresses, set the following
addresses on the service PG:
• MPI address: 0
• Highest MPI address: 126
IN STEP 7, you then determine the highest MPI address on the MPI subnet and match the
highest MPI address in the PG to that of the MPI subnet.
See also
Procedure: Commissioning the hardware (Page 8-1)
Procedure: Software commissioning (Page 8-3)
8.4.5.5 Connecting a PG to ungrounded MPI nodes (not CPU 31xC)
Requirements
The PG must be equipped with an integrated MPI interface or an MPI card in order to
connect it to an MPI.
Connecting a PG to ungrounded nodes on an MPI subnet (not CPU 31xC)
Connecting a PG to ungrounded nodes
Always use an ungrounded PG to connect to ungrounded MPI subnet nodes or to
ungrounded S7-300 PLCs.
Connecting a grounded PG to the MPI
You want to operate with ungrounded nodes. If the MPI at the PG is grounded, you must
interconnect the nodes and the PG with an RS485 repeater. You must connect the
ungrounded nodes to bus segment 2 if the PG is connected to bus segment 1
(terminals A1 B1) or to the PG/OP interface (refer to Chapter 7 in the
Module Data
Reference Manual).

Siemens Simatic S7-300 CPU 31xC Series Specifications

General

Series	S7-300 CPU 31xC
Power Supply	24 V DC
Communication Interfaces	MPI, PROFIBUS DP
Programming Languages	LAD, STL, FBD, SCL
Operating Temperature	0°C to +60°C
Memory	48 KB - 512 KB
Dimensions	40 x 125 x 130 mm (varies by model)