Siemens Simatic S7-300 CPU 31xC Series User Manual

Configuring
4.11 Planning subnets
S7-300, CPU 31xC and CPU 31x: Installation
Operating Instructions, Edition 08/2004, A5E00105492-05
4-31
Number of nodes
Maximum number of nodes per subnet:
Table 4-13 Subnet nodes
Parameters MPI PROFIBUS DP
Number 127 126
1
Addresses 0 to 126 0 to 125
Note Default: 32 addresses
Reserved addresses:
• Address 0 for PG
• Address 1 for OP
of those:
• 1 master (reserved)
• 1 PG connection (address 0 reserved)
• 124 slaves or other masters
1
Note the CPU-specific maximum specifications in the relevant CPU manual.
MPI/PROFIBUS DP addresses
You need to assign an address to all nodes in order to enable intercommunication:
• On the MPI network: an MPI address
• On the PROFIBUS DP network: a PROFIBUS DP address
You can use the PG to set the MPI/PROFIBUS addresses for each one of the nodes (some
of the PROFIBUS DP slaves are equipped with a selector switch for this purpose).
Default MPI/PROFIBUS DP addresses
The table below shows you the default setting of the MPI/PROFIBUS DP addresses, and the
factory setting of the highest MPI/PROFIBUS DP addresses for the nodes.
Table 4-14 MPI/PROFIBUS DP addresses
Node (device) Default
MPI/PROFIBUS DP
address
Default highest MPI
address
Default highest PROFIBUS DP
address
PG 0 32 126
OP 1 32 126
CPU 2 32 126
Rules: Assignment of MPI /PROFIBUS DP addresses
Note the following rules before assigning MPI/PROFIBUS addresses:
• All MPI/PROFIBUS subnet addresses must be unique.
• Highest MPI/PROFIBUS address ≥ physical MPI/PROFIBUS address, and must be
identical for each node. (Exception: connecting a PG to multiple nodes; refer to the next
chapter).

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)