Interfaces - Siemens S7-300 Installation Manual

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Use fiber optic cables instead of copper conductors if you want your field bus to
cover greater distances regardless of the transmission rate and be insensitive to
external noise fields.
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For information on what to take into account relating to equipotential bonding when
you configure your network, refer to the corresponding chapter in the appendix.
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the section referring to communication in the relevant CPU manual.
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MPI (Multi-Point Interface) represents the interface between the CPU and a PG/OP
or for communication in an MPI Subnet.
The typical (default) transmission rate is 187.5 Kbps. You can also set the rate to
19.2 Kbps for communication with an S7-200. Other baud rates are not possible
(exception CPU 318-2DP: up to 12 Mbps).
The CPU automatically broadcasts its bus parameter configuration (e.g.
transmission rate) via MPI interface. A programming device, for example, can then
automatically retrieve the correct parameters and connect to an MPI Subnet.
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In RUN mode, you may only connect PGs to the MPI Subnet.
Other stations (e.g.. OP, TP, ...) should not be connected to the MPI subnet while
the PLC is in run mode. Otherwise, transferred data might be corrupted as a result
of interference or global data packages may get lost.
S7-300 Automation System, Hardware and Installation: CPU 312IFM - 318-2 DP
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