Short summary

Name	`SUB`
→POU type	→function
Category	IEC-block, Numeric
Conform to →IEC-standard	currently restricted (IEC demands data type `ANY_MAGNITUDE` for the inputs and the return value, hence the following data type is demanded as well: `LTIME`. Currently, this data type is not supported for the block.) (IEC demands error handling, if the result of the block exceeds the range of values for the output data type. See " No check of invalid connections " for the behavior in logi.CAD 3. )
Graphical interface
Available since	version 1.0.0 (for logi.CAD 3) – initial variant: `ANY_NUM` for inputs and return value version 1.64.0 (for logi.CAD 3) – enhancement: `TIME` for inputs and return value

Functionality

The mathematical function subtraction is called: The block returns the difference for IN1 – IN2 .

No check of invalid connections

For some blocks, invalid connections are not checked by logi.CAD 3. Therefore, enter code in your application to detect invalid connections (e.g. IF-statements in the ST-code). See "Examples for invalid Connections".

See "IEC-blocks for the application" for information what the consequences of an invalid connection might be.

Inputs, return value

	Identifier	→Data type	Description
Inputs:	`IN1`	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT`, `LINT` oder `TIME`	1st value
Inputs:	`IN2`	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT`, `LINT` oder `TIME`	2nd value
Return value:	–	`REAL`, `LREAL`, `USINT`, `UINT`, `UDINT`, `ULINT`, `SINT`, `INT`, `DINT`, `LINT` oder `TIME`

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

See:

"Blocks for safe logic" whether this block is supported for developing safety-relevant applications.
"Highlighting safe logic in the FBD-editor" for the effects when using the block as a block for safe logic .

Example for usage within ST-editor

PROGRAM Test
   VAR
      result : REAL;
   END_VAR
   result := SUB(IN1 := 4.0, IN2 := 3.0);    (* The variable 'result' evaluates to '1.0'. *)
END_PROGRAM

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.

Examples for invalid connections

An invalid connection due to →overflows or →underflows might occur during a calculation using SUB.

Examples for invalid connections

SUB(IN1 := SINT#100, IN2 := SINT#-50);
   (* Overflow: '100 - -50' would evaluate to '150' but calculates '-106'. Upper limit for SINT is '127'. *)
SUB(IN1 := SINT#-100, IN2 := SINT#50);
   (* Negative overflow: '-100 - 50' would evaluate to '-150' but calculates '106'. Lower limit for SINT is '-128'. *)