Subtract (SUB)

The SUB instruction subtracts Source B from Source A and places the result in the Destination.

Available Languages

-    Ladder Diagram

-    Function Block

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

* There is no equivalent structured text instruction. Use the operator in an expression.

Operands
-    Ladder Diagram

Operand	Type	Format	Description
Source A	SINT INT DINT REAL	Immediate tag	value to subtract to Source B
Source B	SINT INT DINT REAL	immediate tag	value to subtract to Source A
Destination	SINT INT DINT REAL	tag	tag to store the result

-    Function Block

Operand	Type	Format	Description
SUB tag	FBD_MATH	structure	SUB structure

-    Structured Text
Use the minus sign "-" as an operator within an expression. This expression subtracts sourceA from sourceB and stores the result in dest.

dest := sourceA - sourceB;

FBD_MATH 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 from which to subtract SourceB. Valid = any float
SourceB	REAL	Value to subtract from SourceA. Valid = any float

Output Parameter	Data Type	Description
EnableOut	BOOL	Enable output.
Dest	REAL	Result of the math instruction. Arithmetic status flags are set for this output.

Example
Subtract float_value_2 from float_value_1 and place the result in subtract_result.

-    Ladder Diagram

-    Function Block

-    Structured Text

subtract_result := float_value_1 - float_value_2;

File name: PLC-18_IS_CMI-SUB.pdf
File size: 418.93 KB