If one master fails in my multimaster system, are the other systems
still able to communicate?
In your network there are multiple masters that each have access to
multiple slaves. If one master fails, e.g. through power failure or
another technical defect, then the following must be noted:
If the failure of one master in a multimaster system is due to a
hardware fault, then under circumstances the complete network can
be put out of action through a short-circuit on the bus line. In
this case the fault must be cleared and the defective master
removed from the network. If the failure of the master has no
direct effect on the electrical properties (e.g. CP in STOP mode or
power failure of the complete station), then the network can
If the master concerned is the last bus user in the bus
network, then the following must be noted for PROFIBUS/MPI:
The open PROFIBUS line end must always have an active terminating
element, i.e. one to which power is applied. This prevents
reflections (noise or interference signals through periodic and/or
random deviations) on the bus line. This is the only way for the
other stations to be able to continue with unimpaired data
communications. You can use the terminator that is included in the
PROFIBUS connectors, but this has the disadvantage that if the
complete station fails (e.g. through power supply failure), the
network terminator is also lost. Then your complete network fails.
It is better to use an external terminator (MLFB:
6ES7972-0DA00-0AA0), that is independent of the power supply of the
You do not need a terminator for Industrial Ethernet.
If the failed master does not cause a bus short-circuit, then it
does not need to be isolated from the bus. The communication of the
intact master stations with their slaves is not
The other masters can continue to have data communications with
their slaves. The total cycle time is even shortened by the bus
access time of the failed master.