Rockwell Automation Logix5000 Controllers Sequential Function Charts Programming Manual - Manual (Page 46)

Chapter 1 Design a sequential function chart
• The X bit of the stop element turns on. This signals that the SFC is at the
stop element.
• Stored actions remain active.
• Execution stops for part or all of the SFC.
If the stop element is at the end of a Then
• Sequence
• Selection branch The entire SFC stops
• Path within a simultaneous branch Only that path stops while the rest of the SFC continues to
execute.
Example
Use a stop element on page 45
When the SFC reaches last_step and process_done is TRUE, the execution of the
SFC stops.
Restart (reset) the SFC
Once at the stop element, you have several options to restart the SFC.
If the SFC is And the Last Scan of the Active Steps
option is
Then
Nested (i.e., another SFC calls this SFC as a
subroutine)
• Automatic reset
At the end of the step that calls the nested SFC, the nested SFC automatically resets.
• The nested SFC resets to the initial step.
• The X bit of the stop element in the nested SFC clears to zero.
• Programmatic reset
• Don’t scan
1. Use an SFC Reset (SFR) instruction to restart the SFC at the required step.
2. Use logic to clear the X bit of the stop element.
Not nested (i.e., no SFC calls this SFC as a
subroutine)
-------------------------------> 1. Use an SFC Reset (SFR) instruction to restart the SFC at the required step.
2. Use logic to clear the X bit of the stop element.
46 Rockwell Automation Publication 1756-PM006F-EN-P - October 2014