Structure - Mitsubishi Electric MELSEC iQ-F Series Programming Manual

8.2

Structure

Basic operation of SFC
An SFC program starts at an initial step, executes the next step every time the relevant transition becomes TRUE, and ends a
series of operations at an end step.
(1)
(2)
(3)
(4)
(5)
(6)
1.
When starting a block, the initial step (1) is activated first and then the action (2) is executed. After execution of the action
(2), the program checks whether the next transition (3) has become TRUE.
2.
The program executes only the action (2) until the transition (3) becomes TRUE. When the transition (3) becomes TRUE,
the program ends the action (2), deactivates the initial step (1), and activates the next normal step (4).
3.
After execution of the action of the normal step (4), the program checks whether the next transition has become TRUE. If
the next transition does not become TRUE, the program repeats the execution of the action of the normal step (4).
4.
When the transition becomes TRUE, the program ends the action, deactivates the step (4), and activates the next step
(5).
5.
Every time the transition becomes TRUE, the program activates the next step and ends the block when it finally activates
the end step (6).
• Up to 4 actions can be created in one step. When multiple actions are created, they will be executed in
order from the top. (Page 84 Action)
• The operation of the initial step and normal step can be changed by adding the attribute. (Page 77 Step
types)
8 SFC PROGRAM
74
8.2 Structure
(1) Initial step
(2) Action
(3) Transition
(4) Normal step
(5) Normal step
(6) End step