Sequential Function Chart（Sfc - SMB MAT-LC-C Series User Manual

REPEAT Loop
The difference between a REPEAT loop and a WHILE loop is that its break condition is checked
after the loop executes, which means that the loop executes at least once, regardless of the
break condition.
Sentence:
REPEAT
<Instructions>
UNTIL <Boolean expression>
END_REPEAT;
Instructions are executed until the Boolean expression returns TRUE. If the Boolean expression
is assigned a true value for the first time, the Instructions are executed only once, otherwise the
Instructions will be executed repeatedly and will cause a time delay.
<Note> The programmer can ensure that no infinite loop occurs by changing the condition of the
instruction part of the loop, for example, by incrementing or decrementing the counter.
Example：
REPEAT
Var1 ：= Var1*2
Counter ：= Counter-1；
UNTIL
Counter=0
END_REPEAT；
EXIT Instruction
f there is an EXIT instruction in a FOR, WHILE or REPEAT loop, then the inner loop ends,
regardless of the interrupt condition.
6.2.3 Sequential Function Chart（SFC）
Sequential function chart is a graphical language that can be used to describe the sequence of
different actions in a program. Because these actions are assigned to single-step elements, and
transition variables are used to control the order of processing.
Step
A POU written in a sequential function diagram contains a series of steps, which are realized
through directed connections (transition conditions).
There are two types of steps:
• Simple type: Each step consists of an action and a flag to indicate whether the step is active or
not. If a single step action is in progress, a small triangle will appear in the upper right corner of
the step.
• IEC Types: Actions or Boolean variables with each step consisting of a flag and one or more
assignments. The associated action appears to the right of the step.
Action
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