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).