Lenze DDS v2.0 - Manual (Page 15)

Introduction to IEC 61131-3 programming
Programming languages
13
l
DDS-IEC61131 EN 2.0
5.2 Structured Text (ST)
(Structured Text)
Structured Text consists of instructions which can be executed like in high languages with
conditions (IF..THEN..ELSE) or in loops (WHILE..DO).
Structured Text is an easily readable and understandable programming language that does not only
offer powerful loop programming and the possibility of conditioned commands but also imaging
mathematical functions.
Example:
IF value < 7 THEN
WHILE value < 8 DO
value := value + 1;
END_WHILE ;
END_IF ;
Instructions (overview)
Type of instruction Example
Assignment by assignment operator
A:=B;
CV:=CV + 1;
C:=SIN(X);
Call of a function block,
use of an FB
CMD_TMR(IN:=%IX5, PT:=300);
A:=CMD_TMR.Q
RETURN RETURN ;
IF
condition
D:=B*B;
IF
D<0.0 THEN
C:=A;
ELSIF D=0.0 THEN
C:=B;
ELSE
C:=D;
END_IF
;
CASE
selection
CASE INT1 OF
1: BOOL1:=TRUE;
2: BOOL2:=TRUE;
ELSE
BOOL1:=FALSE;
BOOL2:=FALSE;
END_CASE ;
FOR
loop
J:=101;
FOR
I:=1 TO 100 BY 2 DO
IF ARR[I]=70 THEN
J:=I;
EXIT;
END_IF;
END_FOR ;
WHILE
loop
J:=1;
WHILE
J<=100 AND ARR[J]<>70 DO
J:=J+2;
END_WHILE ;
REPEAT
loop
J:=-1;
REPEAT
J:=J+2;
UNTIL J= 101 OR ARR[J]=70
END_REPEAT ;
EXIT EXIT ;
Empty instruction ;
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