GE GFK-0787B GMR Discrepancy Reporting, Discrete Input Discrepancy Reporting, Input Data

5

GMR Discrepancy Reporting

The GMR software performs discrepancy reporting for:

HVoted discrete inputs

HDiscrete outputs

HAnalog inputs

There is no discrepancy reporting for analog outputs.

Discrete Input Discrepancy Reporting

As explained in the chapter on PLC operation, the PLC compares corresponding inputs from bus A, bus B, and bus C, and performs voting:

	Field Input Data		PLC Performs	Single Input Provided
			2 out of 3 Voting	to Application Logic
Input A		0

Input B

0

0

Input C

1

If there is a discrepancy between any original input data value for an input and its voted input state, the PLC automatically places a message in the I/O Fault Table, where it is available to the Logicmaster 90 software and the application program logic. Discrepancy faults are latched.

When a discrepancy occurs, the PLC sets the fault contact for that voted input. See page 5-25 for information about these fault contacts.

Discrepancy signals are filtered for the configured input discepancy filter time to eliminate transient discrepancies caused by timing differences.

The following table shows possible discrepancies between the input data and voted input data.

	Input Data
A	B
0	0
0	0
0	1

01

10

1 0

11

11

C

0

1

0

1

0

1

0

1

Voted		Discrepancy
Inputs	A	B	C
0	0	0	0
0	0	0	1
0	0	1	0
1	1	0	0
0	1	0	0
1	0	1	0
1	0	0	1
1	0	0	0

GFK-0787B Chapter 5 Diagnostics 5-11