PLC Programming

IEC Operators and additional norm extending functions
Note:
If you define functions in your project with the names CheckDivByte, CheckDivWord,
CheckDivDWord and CheckDivReal, you can use them to check the value of the divisor if you use
the operator DIV, for example to avoid a division by 0. The functions must have the above listed
names.
See in the following an example for the implementation of function CheckDivReal:
Example for the implementation of the function CheckDivReal:
FUNCTION CheckDivReal : REAL
VAR_INPUT
divisor:REAL;
END_VAR
IF divisor = 0 THEN
CheckDivReal:=1;
ELSE
CheckDivReal:=divisor;
END_IF;
Operator DIV uses the output of function CheckDivReal as divisor. In a program like shown in the
following example this avoids a division by 0, the divisor (d) is set from 0 to 1. So the result of the
division is 799.
PROGRAM PLC_PRG
VAR
erg:REAL;
v1:REAL:=799;
d:REAL;
END_VAR
erg:= v1 DIV d
MOD
Modulo Division of one variable by another of the types: BYTE, WORD, DWORD, SINT, USINT, INT,
UINT, DINT, UDINT. The result of this function will be the remainder of the division. This result will be
a whole number.
Example in IL:
LD 9
MOD 2
ST Var 1 (* Result is 1 *)
Example in ST:
var1 := 9 MOD 2;
Example in FBD:
MOVE
Assignment of a variable to another variable of an appropriate type. As MOVE is available as a box in
the graphic editors FBD, LD, CFC, there the (unlocking) EN/EN0 functionality can also be applied on a
variable assignment.
Example in CFC in conjunction with the EN/EN0 function:
Only if en_i is TRUE, var1 will be assigned to var2.
Example in IL:
CoDeSys V2.3 10-3