Rockwell Automation Logix5000 Controllers Sequential Function Charts Programming Manual - Manual (Page 26)

Chapter 1 Design a sequential function chart
To program a non-Boolean action, you have these options.
If you want to Then
• Execute your logic without additional routines
• Use structured text assignments, constructs, and
instructions
Embed structured text.
When the S_Complete_the_Batch step is active, the S_Open_Outlet action executes. The action sets the
Outlet.ProgCommand tag equal to 1, which opens the outlet valve.
• Re-use logic in multiple steps
• Use another language to program the action, such as
ladder logic
• Nest an SFC
Call a subroutine.
When the S_Complete_the_Batch step is active, the S_Open_Outlet action executes. The action calls the
Open_Outlet routine.
Open_Outlet Routine
When the Open_Outlet routine executes, the OTE instruction sets the Outlet.ProgCommand tag equal to 1, which
opens the outlet valve.
You cannot reuse a non-Boolean action within the same SFC except to reset a
stored action. Only one instance of a specific non-Boolean action is permitted per
SFC.
Use a Boolean action
A Boolean action contains no logic for the action. It simply sets a bit in its tag
(SFC_ACTION structure). To do the action, other logic must monitor the bit
and execute when the bit is on.
With Boolean actions, you have to manually reset the assignments and
instructions that are associated with the action. Since there is no link between the
action and the logic that performs the action, the automatic reset option does not
affect Boolean actions.
26 Rockwell Automation Publication 1756-PM006F-EN-P - October 2014