GE GFK-0787B user manual Input Subsystem, PLC Subsystem Voting on Input Data

1

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:

A B C

Closed (1) 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

input B

input C

1

1

0

voted

input	input A
1	input B
	input C

1

1

0

voted	input A
input
1	input B
	input C

1

1

0

voted input

1

PLC APLC BPLC C

If an input is faulty, the PLC(s) follow a configurable, predetermined voting scheme based on the remaining input data.

1-6	GeniustModular Redundancy Flexible Triple Modular Redundant (TMR) System	GFK-0787B
	User's Manual ± March 1995