GE GFK-0787B Analog Input Voting

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4-13GFK-0787B Chapter 4 PLC Subsystem
Analog Input Voting
Immediately after the input scan, before the application program execution begins, the
GMR software performs input voting. It automatically reads and votes on the three sets
of data in areas A, B, and C of the analog Input Table. How it does the voting is
described below. It places the resulting voted input value into the voted inputs area of
the Input Table.
If a failure (discrepancy fault, or Genius fault) occurs, the GMR software rejects the
faulty data. Depending on the configuration of the input group, input voting may go
from three inputs to two inputs to one input, or from three inputs to two inputs to the
configured default value.
Field Input Data
Input 1
Input 2
Input 3
152
150
110
150
Single Input Provided
to Application Logic
Field Input
Data
Duplex State
Default State
low, high,
or average
hold last,
minimum, or
maximum
In addition to field input data, the GMR software may also make use of the input
group’s configured Duplex State and Default State in determining the final input value
to provide to the PLC.
The Duplex State is a “tiebreaker” value that is used when there are two
field inputs present. The Duplex State may be configured as the higher
actual input value, the lower value, or an average of the two.
The Default State is the value that will be provided directly to the PLC
instead of a voted input value if the following inputs fail:
The single input in a Simplex group.
The remaining input in a Duplex or Triplex group configured for
3–2–1–0 Voting Adaptation.
Either of the two inputs to a Duplex group configured for 3–2–0
Voting Adaptation.
Either of the two remaining inputs to a Triplex group configured for
3–2–0 Voting Adaptation.
The Default State can be configured as the last input state, or a specified
maximum or minimum value.
Duplex State
Default State