Rockwell-automation Logix5000 Controllers Sequential Function Charts P Manual de usuario descargar pdf (Pagina 37)

Design a sequential function chart Chapter 1

The following table compares the different options for handling the last scan of a

step.

Characteristic During the last scan of a step, this option does

Don’t scan Programmatic reset Automatic reset

Execution actions

Only P and P0 actions execute. They execute

according to their logic.

All actions execute according to their logic.

•

P and P0 actions execute according to

their logic.

• All other actions execute in Postscan

mode.

• On the next scan of the routine, the P and

P0 actions execute in Postscan mode.

Retention of data values All data keeps its current values. All data keeps its current values.

• Data reverts to its values for postscan.

• Tags to the left of [:=] assignments clear

to zero.

Method for clearing data Use P and P0 actions. Use either of these.

• Status bits of the step or action to

condition logic

• P and P0 actions

Use either of these.

• [:=] assignment (non-retentive

assignment)

• Instructions that clear their data during

postscan

Reset of a nested SFC A nested SFCs remains at its current step. A nested SFCs remains at its current step.

For the Restart Position property, if you

choose the Restart at initial step option,

then these occur.

• A nested SFC resets to its initial step

• The X bit of a stop element in a nested SFC

clears to zero

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Rockwell-automation Logix5000 Controllers Sequential Function Charts P Manual de usuario Pagina 37