The ‎FOR‎ loop is used to execute instructions with a certain number of repetitions.

Syntax:

FOR <counter> := <start value> TO <end value> {BY <increment> } DO
<instructions>
END_FOR;

The section inside the curly parentheses {} is optional.

CODESYS executes the ‎<instructions>‎ as long as the ‎<counter>‎ is not greater, or - in case of negative increment - is not smaller than the ‎<end value>‎. This is checked before the execution of the ‎<instructions>‎.

Every time the instructions ‎<instructions>‎ have been executed, the counter ‎<counter>‎ is automatically increased by the increment ‎<increment>‎. The increment ‎<increment>‎ can have any integral value. If you do not specify an increment, the standard increment is ‎1‎.

FOR iCounter := 1 TO 5 BY 1 DO
iVar1 := iVar1*2;
END_FOR;
Erg := iVar1;

CAUTION

The end value <end value> may not attain the same value as the upper limit of the data type of the counter.

If the end value of the counter is equal to the upper limit of the data type of the counter, an endless loop results. For example, an endless loop results in the above example if ‎iCounter‎ is of the data type ‎SINT‎ and the ‎<end value>‎ equals ‎127‎, since the data type ‎SINT‎ has the upper limit ‎127‎.

As an extension to the IEC 61131-3 standard you can use the ‎CONTINUE‎ instruction within the ‎FOR‎ loop.