SUB block

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 Neuron Power Engineer.)
Graphical interface
Available since	version 1.0.0 (for Neuron Power Engineer) – initial variant: `ANY_NUM` for inputs and return value version 1.64.0 (for Neuron Power Engineer) – 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 Neuron Power Engineer. 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

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'. *)`

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'. *)