Nest an sfc – Rockwell Automation Logix5000 Controllers Sequential Function Charts Programming Manual User Manual

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Chapter 1 Design a sequential function chart

One method for organizing your project is to create one SFC that provides a

high-level view of your process. Each step of that SFC calls another SFC that

performs the detailed procedures of the step (nested SFC).

This figure shows one way to nest an SFC. In this method, the last scan option of

the SFC is configured for either Programmatic reset or Don’t Scan. If you

configure the SFC for Automatic reset, then step 1 in is unnecessary.

Reset the nested SFC.
• The SFR instruction restarts SFC_b at SFC_b_Step_1. Each time SFC_a leaves this step and then returns,

you have to reset SFC_b.

• The action also clears the X bit of the stop element.

Call SFC_b.

Stop SFC_b. This sets the X bit of the stop element.

Use the X bit of the stop element to signal that SFC_b is done and it is time to go to the next step.

Nest an SFC

Rockwell Automation Publication 1756-PM006F-EN-P - October 2014