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1-6 Genius Modular Redundancy Flexible Triple Modular Redundant (TMR) System
User’s Manual – March 1995
GFK-0787B
Input Subsystem
In a GMR system, the basic elements of an input subsystem are single or triple sensors
connected to triple Genius blocks. Each block is on a different communications bus
(shown below as A, B, and C).
For this example, there are triple input sensors which are normally-on. However, one of
these input sensors is off:
Closed (1)
ABC
Open (0)
Each PLC in the example system votes on the input data received from these three
sensors as summarized below. For a more detailed description of input processing, see
chapter 2.
PLC Subsystem: Voting on Input Data
The example system uses three PLCs. Each PLC receives corresponding inputs from all
three blocks in the input group.
The GMR software in each PLC automatically votes on the input data and provides the
voted input to the application program (the program can also access the unvoted input
data). Each of these example voted inputs represents the same input sensors.
input A
1
input B
1
input C
0
voted
input
1
input A
1
input B
1
input C
0
voted
input
1
input A
1
input B
1
input C
0
voted
input
1
PLC A PLC CPLC B
If an input is faulty, the PLC(s) follow a configurable, predetermined voting scheme
based on the remaining input data.