Omron WS02-CXPC1-V8 - V8.1 REV 02-2009 Operation Manual page 73

Elements of SFC
• If an action is used in more than one step, it will be displayed in parentheses from
the second occurrence on to indicate that it is used more than once.
Flags Indicating the Execution Status of Actions
There are two kinds of flags that indicate an action's execution status. Both kinds of
flags are changed by the step's active/inactive status, and both can be used as bits in
ladder and ST programs.
Action Flag Q (Action_name.Q)
This flag is ON when the step is active, and goes OFF when the step is inactive.
This flag can be used as an input condition in a ladder or ST program to prevent
execution of a process when a step is deactivated. The flag can also be used as an
input condition in an ST program when resetting outputs.
Action Flag A (Action_name.A)
This flag is ON when the step is active, and goes OFF when execution of the final scan
is completed after the step is deactivated.
Use the Action Flag A as a set with the Action Flag Q when special processing must be
performed for the final scan in a ladder or ST program.
The following diagram shows the operation of the action flags when the final scan
function was enabled by selecting the Apply Final Scan Logic Option in the General
Tab of the SFC program's Property Dialog Box.
Step
Action Qualifier = N
The following diagram shows the operation of the action flags when the final scan
function was disabled by clearing the Apply Final Scan Logic Option on the General
Tab Page of the SFC program's Property Dialog Box.
ON
OFF
ON
Action flag Q
(Action_name.Q)
OFF
ON
Action flag A
(Action_name.A)
OFF
Executed
Action
Not executed
Active status
1 scan (cycle)
Normal End
processing processing
Section 2-3
57