Rockwell-automation Logix5000 Controllers Sequential Function Charts P Manuale Utente Scaricare il pdf (Pagina 20)

Chapter 1 Design a sequential function chart

This diagram shows the relationship of the X, FS, SA, and LS bits.

Once you define the steps of your process, organize them into sequences,

simultaneous branches, selection branches, or loops.

To Use this structure With these considerations

Execute 1 or more steps in sequence

• One executes repeatedly

• Then the next executes repeatedly

Sequence on page 22

The SFC checks the transition at the end of the step.

• If TRUE the SFC goes to the next step.

• If FALSE, the SFC repeats the step.

• Choose between alternative steps or groups of steps

depending on logic conditions

• Execute a step or steps or skip the step or steps

depending on logic conditions

Selection Branch on page 22

• It is OK for a path to have no steps and only a transition.

This lets the SFC skip the selection branch.

•

By default, the SFC checks from left to right the transitions

that start each path. It takes the first TRUE path.

• If no transitions are TRUE, the SFC repeats the previous

step.

• The Logix Designer application lets you change the order in

which the SFC checks the transitions.

Execute 2 or more steps at the same time. All paths must

finish before continuing the SFC

Simultaneous Branch on page 23

• A single transition ends the branch.

• The SFC checks the ending transition after the last step in

each path has executed at least once. If the transition is

FALSE, the SFC repeats the previous step.

Organize the steps

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

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Rockwell-automation Logix5000 Controllers Sequential Function Charts P Manuale Utente Pagina 20