Basics; Subnet Nodes; Mpi/Profibus-Dp Addresses - Siemens SIMATIC S7-300 Hardware And Installation Manual

Configuring
4.10.2

Basics

MPI, PROFIBUS-DP, PtP
Since these subnets are the most commonly used for S7-300 CPUs, we shall take
a closer look at them.
Declaration: Device = Node
In the following, all networked devices are referred to as nodes.
Segment
A segment is a bus link between two terminating resistors. A segment can include
up to 32 nodes. It is also limited by the permissible line length, depending on the
transmission rate.
Transmission rate
These maximum transmission rates are possible:
• MPI
12 Mbps with CPU 318-2 DP
–
187.5 Kbps with all other CPUs
–
• PROFIBUS-DP: 12 Mbps
• PtP:
Half duplex: 38.4 Kbps
–
Full duplex: 19.2 Kbps
–
Number of nodes
Maximum possible number of nodes per subnet:
Table 4-11
Parameter
Number
Addresses
Remarks
1) Note CPU-specific maximum specifications in the respective CPU manual.

MPI/PROFIBUS-DP addresses

To ensure that all nodes can intercommunicate, you must assign them an address:
• In the MPI network: an "MPI address"
•
In the PROFIBUS-DP network: a "PROFIBUS-DP address"
4-30

Subnet nodes

MPI
127
0 to 126
Default: 32 addresses
Reserved are:
•
address 0 for PG
•
address 1 for OP
S7-300 Programmable Controller Hardware and Installation
PROFIBUS-DP
1)
126
0 to 125
of those:
•
1 Master (reserved)
•
1 PG connection
(address 0 reserved)
•
124 slaves or other
masters
PtP
2
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