SUB

Subtracts Value2 from Value1 and stores the result in Result.

Ladder Representation

Block Structure

Variable Type	Name	Data Type	Description
VAR_INPUT	EN	BOOL	Block enabling.
VAR_INPUT	Value1	BYTE USINT SINT WORD UINT INT DWORD UDINT DINT REAL	Minuend of the operation.
VAR_INPUT	Value2	BYTE USINT SINT WORD UINT INT DWORD UDINT DINT REAL	Subtrahend of the operation.
VAR_OUTPUT	Done	BOOL	End of operation.
VAR_OUTPUT	Result	BYTE USINT SINT WORD UINT INT DWORD UDINT DINT REAL	Variable that stores the operation result.

Operation

When EN is TRUE, the block writes the subtraction result between Value1 and Value2 to Result.

If the operation completes without errors, Done is set. If an operation error occurs, Done remains FALSE and Result keeps its previous value.

When EN is FALSE, Result remains unchanged and Done remains FALSE.

Execution Flowchart

Examples

Ladder Example

This example subtracts VALUE2 from VALUE1 and stores the final result in RESULT.

This example subtracts VALUE2 from VALUE1 and stores the final result in RESULT. The block accepts arguments with different signs.

This example subtracts VALUE2 from VALUE1. The final result, 141, cannot be stored in RESULT because it is outside the accepted range for SINT. For this reason, RESULT remains unchanged and the output is disabled.

Structured Text Example

The following Structured Text code applies the same logic shown in the Ladder example.

Structured Text

VAR
    VALUE1 : SINT := 52;
    VALUE2 : SINT := -17;
    RESULT : SINT;
END_VAR

RESULT := FB_SUB(
    EN:=DI1,
    Value1:=VALUE1,
    Value2:=VALUE2,
    Done=>DO1);