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3.12 Fault Behavior
3.12.1 Field Bus Failure
A field bus failure is given when the master cuts-out or the bus cable is
interrupted. A fault in the master can also lead to a field bus failure.
The red BF-LED lights up.
The failure of the field bus can activate the parameterizable substitute value of
the I/O modules. During projecting of the inputs and outputs a substitute value
can be laid down for each channel.
Substitute Value
Strategy
Minimum value
Maximum value
Substitute value
PFC takes over
Stop internal bus
The values are entered in the output process image by the coupler. With the
I/O modules with byte orientated data width, e.g. with the pulse width module,
the substitute value is determined via the value range.
The process data is transmitted as soon as the field bus is active again and the
outputs in the node are set accordingly.
3.12.2 Internal Bus Fault
An internal bus fault is created, for example, if an I/O module is removed. If
this fault occurs during operation the output modules behave in the same
manner as an I/O module stop. The input process image is set in accordance
with the projected strategy.
The I/O-LED blinks red. The slave generates a detailed diagnostics message.
Once the internal bus fault has been overcome the coupler starts up again
automatically in accordance with the parameterized restart behavior. The
transfer of the process data is then resumed and the node outputs are
correspondingly set.
WAGO-I/O-SYSTEM 750
Bus System
Programmable Field Bus Controller 750-833
Value (Bit orientated)
Digital Output Modules
0
1
0 or 1
The local PFC application takes over the output data
Behavior determined by I/O module
Fault Behavior
Value (Byte orientated)
Digital Input Modules
0 or 4 mA, 0 V
20 mA, 10 V
0/4 ... 20 mA, -10 ... +10 V
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