GE GFK-0787B user manual Output Processing, Discrete Outputs

4

Output Processing

For outputs, the PLC does not perform ªredundancyº voting. Instead, voting is done by the specified types of discrete output block groups. Analog blocks do not provide redundancy voting or autotest features. Both discrete and analog Genius blocks can be used in the output subsystem as non-GMR blocks, however.

Discrete Outputs

As it does for inputs, the GMR software uses separate areas of the Output Table for non-voted outputs, fault-tolerant outputs and copies of the fault-tolerant outputs.

After the application program executes, the GMR software processes discrete output data as described below.

HThe application program places outputs into the discrete Output Table. Data for blocks that are included in the GMR configuration is placed at the start of the output table. In the illustration below, the application program outputs for redundant blocks are labelled ªlogic outputsº. This data is followed by outputs for non-voted blocks.

HThe GMR software copies these logic output into the bottom portion of the Output Table. This data, shown as Fault-tolerant Outputs in the illustration below, is used for physical outputs for the blocks. This separation of physical outputs from logical outputs prevents disruption of outputs such as latches and seal circuits during autotesting.

HDuring the output scan portion of the CPU sweep, the CPU sends the non-voted outputs plus the copied fault-tolerant outputs to the Genius blocks.

Application

Program

GMR

Logic

Discrete Output Table

Logic Outputs

Available for

Simplex Outputs

Reserved memory

Fault-tolerant Outputs

Non-voted Outputs

Fault-tolerant

Output

Devices

GFK-0787B Chapter 4 PLC Subsystem 4-17