Rockwell Automation Logix5000 Controllers Sequential Function Charts Programming Manual - Manual (Page 50)

Chapter 1 Design a sequential function chart
Select the Execute until FALSE transition option only when either of these are
true:
• You do not have to update JSR parameters before each step. Parameters
update only when the SFC returns to the JSR.
• A FALSE transition occurs within the watchdog timer for the task. If the
time that it takes to return to a JSR and complete the rest of the task is
greater than the watchdog timer, a major fault occurs.
Two optional instructions are available that give you further control over the
execution of your SFC.
If you want to Then use this instruction
Pause an SFC Pause SFC (SFP)
Reset an SFC to a specific step or stop Reset SFC (SFR)
Both instructions are available in the ladder logic and structured text
programming languages.
The following diagrams show the execution of an SFC with different
organizations of steps or different selections of execution options.
• Execution of a sequence
• Execution of a simultaneous branch
• Execution of a selection branch
• When parameters enter and exit an SFC
• Options for execution control
Pause or reset an SFC
Execution diagrams
50 Rockwell Automation Publication 1756-PM006F-EN-P - October 2014