ISPSoft User Manual

Chapter 12 Sequential Function Chart
The step name is displayed here.
Users can select qualifiers for the actions associated with the step.
Users can specify qualifiers related to time.
Users can select actions which are qualified.
Users can make comments on the step.
12.2.6.1 Qualifier Types
• N (Normal)
When a step is activated, the N action associated with the step is executed. When the step is
inactivated, the system executes a final scan to disable all the outputs in the N action. However,
the outputs which use the instructions similar SET are not disabled. The actions in the program in
a DVP series PLC are N actions.
• S (Set)
When a step is activated, the S action associated with the step is executed. Even if the step is
inactivated, the S action will still be executed.
When STEP_1 in the figure below is activated, Action1 and Action2 are executed. When Tran1 is
true, STEP_1 becomes inactive. Once STEP_1 is inactivated, the execution of Action1 will stop,
the system will execute a final scan, and Action2 will still be executed.
• D (Delay)
The D action associated with a step is not executed at the time when the step is activated. The
execution of the D action is delayed for a certain amount of time. If the transition following the
step becomes true before the D action is executed, the step will be inactivated, control will be
passed to the next step, and the D action will not be executed. When the step is activated again,
the delay is measured again.
Action1 in the figure below is not executed at the time when STEP_1 is executed. The execution
of Action1 is delayed for two seconds. If STEP_1 is inactivated before Action1 is executed,
Action1 will not be executed.
• SD (Set Delay)
The SD action associated with a step is not executed at the time when the step is activated. The
execution of the SD action is delayed for a certain amount of time. If the SD action is executed, it
will still be executed after the step is inactivated. Besides, if the transition following the step
becomes true before the SD action is executed, control will be passed to the next step, and the
delay will still be measured. A certain amount of time has elapsed before the SD action is
executed.
• DS (Delay Set)
A DS action is similar to a SD action. However, if the transition following a step becomes true
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