Less Than (LES)

The LES instruction tests whether Source A is less than Source B.

Available Languages
-    Ladder Diagram


-    Function Block


-    Structured Text
 This instruction is not available in structured text. *

* There is no equivalent structured text instruction. Use other structured text programming to achieve the same result.

Operands
-    Ladder Diagram
Operand
Type
Format
Description
Notes
Source A
SINT
INT
DINT
REAL
String type

Immediate
tag
value to test against Source B
If you enter a SINT or INT tag, the value converts to a DINT value by sign-extension.

String types are:
-          default STRING data type
-          any new string type you create

To test the characters of a string, enter a string type for both Source A and Source B.
Source B
SINT
INT
DINT
REAL
String type
Immediate
tag
value to test against Source A

-    Function Block
Operand
Type
Format
Description
LES tag
FBD_COMPARE
structure
LES structure

-    Structured Text
Use the less than sign "<" as an operator within an expression. This expression evaluates whether sourceA is less than sourceB.

IF sourceA < sourceB THEN
 <statements>;

FBD_COMPARE Structure
Input Parameter
Data Type
Description
EnableIn
BOOL
Enable input. If cleared, the instruction does not execute and outputs are not updated.
Default is set.
SourceA
REAL
Value to test against SourceB
Valid = any float
SourceB
REAL
Value to test against SourceA
Valid = any float

Output Parameter
Data Type
Description
EnableOut
BOOL
Enable output.
Dest
BOOL
Result of the instruction. This is equivalent to rung-condition-out of the ladder diagram LES instruction.

Example
If value_1 is less than value_2, set light_3. If value_1 is greater than or equal to value_2, clear light_3.

-    Ladder Diagram


-    Function Block

-    Structured Text
light_3 := (value_1 < value_2);


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