Siemens Simatic S7-300 CPU 31xC and CPU 31x S7-300 - Manual (Page 29)

CPU 31xC and CPU 31x, Technical data
Manual, Edition 08/2004, A5E00105475-05
3-1
Communication
3
3.1 Interfaces
3.1.1 Multi-Point Interface (MPI)
Availability
All CPUs described in this manual are equipped with an MPI interface X1.
A CPU equipped with an MPI/DP interface is configured and supplied as MPI. To use the
DP interface, set DP interface mode in STEP 7.
Properties
The MPI (Multi-Point Interface) represents the CPU interface for PG/OP connections, or for
communication on an MPI subnet.
The typical (default) transmission rate of all CPUs is 187.5 kbps. You can also set 19.2 kbps
for communication with an S7-200. The 315-2 PN/DP and 317 CPUs support transmission
rates up to 12 Mbps.
The CPU automatically broadcasts its bus configuration via the MPI interface (the
transmission rate, for example). A PG, for example, can thus receive the correct parameters
and automatically connect to a MPI subnet.
Note
You may only connect PGs to an MPI subnet which is in RUN.
Other stations (for example, OP, TP, ...) should not be connected to the MPI subnet while
the system is in RUN. Otherwise, transferred data might be corrupted as a result
interference, or global data packages may be lost.