GE GFK-0787B Discrete Inputs, Types of Blocks in the Input Subsystem, Discrete Input Processing

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Discrete Inputs

Types of Blocks in the Input Subsystem

The following discrete block versions can be configured for GMR version 2.06 operation and used as GMR input blocks:

24/48VDC16-Circuit Source block:	IC660BBD020M or later
24/48VDC16-Circuit Sink block:	IC660BBD021M or later
12/24VDC32-Circuit Source block:	IC660BBD024N or later
5/12/24VDC32-Circuit Sink block:	IC660BBD025N or later

All types of Genius blocks can be used as non-GMRblocks in a GMR system.

Note that the GMR Input Autotest feature requires point 16, so if the system uses Input Autotest, point 16 is not available as an I/O point for the application (leaving either 15 or 31 points available on the blocks listed above).

Discrete Input Processing

Discrete input processing is handled in each PLC, by the GMR system software. The manner in which inputs are handled depends upon whether a block is included in the GMR configuration, and if it is, upon whether it is part of a 3-block, 2-block, or 1-block group. Input processing by the PLC is explained in detail in the PLC chapter. In general, the GMR system software compares input data from all corresponding inputs (3, 2, or 1) for each point, and provides a voted input result for use by the application program. If all the input data is not available, the GMR system software follows a configured voting adaptation scheme. The application program can also access the original, unvoted input data, along with any non-GMR inputs that have been included in the input subsystem.

Field Input Data		Single Input Pro-
Input A	0	vided to Applica-
			tion Logic
Input B	0		0
		GMR Software Performs
Input C	1
		2 out of 3 Voting

Discrepancy Reporting for GMR Inputs

For GMR inputs, if there is a discrepancy between the original input data for an input and the voted input state, the GMR software automatically places a message in the I/O Fault Table, where it is available to the Logicmaster 90 software and the application program logic. This is also described in more detail in the PLC chapter. Fault bits are also set for input discrepancies. These fault bits are available for use in the application program, for further annunciation or corrective action.

Discrepant signals are filtered for a configurable time period, to eliminate transient discrepancies caused by timing differences.

GFK-0787B Chapter 2 Input Subsystem 2-5