How to Use a Function or a Function Block in ST Language

General Information

This part explains how to implement a Function and a Function Block in ST language.

Function SetRTCDrift and Function Block TON are used as examples to show implementations.

Using a Function in ST Language

This procedure describes how to insert a function in ST language:

Step	Action
1	Open or create a new POU in Structured Text language. NOTE: The procedure to create a POU is not detailed here. For more information, refer to Adding and Calling POUs.
2	Create the variables that the function requires.
3	Use the general syntax in the POU ST Editor for the ST language of a function. The general syntax is: FunctionResult:= FunctionName(VarInput1, VarInput2,.. VarInputx);

Step

Action

Open or create a new POU in Structured Text language.

NOTE: The procedure to create a POU is not detailed here. For more information, refer to Adding and Calling POUs.

Create the variables that the function requires.

Use the general syntax in the POU ST Editor for the ST language of a function. The general syntax is:

FunctionResult:= FunctionName(VarInput1, VarInput2,.. VarInputx);

To illustrate the procedure, consider the function SetRTCDrift graphically presented below:

Function	Graphical Representation
SetRTCDrift

Function

Graphical Representation

SetRTCDrift

The ST language of this function is the following:

Function	Representation in SoMachine POU ST Editor
SetRTCDrift	PROGRAM MyProgram_ST VAR myDrift: SINT(-29..29) := 5; myDay: DAY_OF_WEEK := SUNDAY; myHour: HOUR := 12; myMinute: MINUTE; myRTCAdjust: RTCDRIFT_ERROR; END_VAR myRTCAdjust:= SetRTCDrift(myDrift, myDay, myHour, myMinute);

Function

Representation in SoMachine POU ST Editor

SetRTCDrift

PROGRAM MyProgram_ST
VAR myDrift: SINT(-29..29) := 5;
myDay: DAY_OF_WEEK := SUNDAY;
myHour: HOUR := 12;
myMinute: MINUTE;
myRTCAdjust: RTCDRIFT_ERROR;
END_VAR

myRTCAdjust:= SetRTCDrift(myDrift, myDay, myHour, myMinute);

Using a Function Block in ST Language

This procedure describes how to insert a function block in ST language:

Step	Action
1	Open or create a new POU in Structured Text language. NOTE: The procedure to create a POU is not detailed here. For more information on adding, declaring and calling POUs, refer to the related documentation.
2	Create the input and output variables and the instance required for the function block: oInput variables are the input parameters required by the function block oOutput variables receive the value returned by the function block
3	Use the general syntax in the POU ST Editor for the ST language of a Function Block. The general syntax is: FunctionBlock_InstanceName(Input1:=VarInput1, Input2:=VarInput2,... Ouput1=>VarOutput1, Ouput2=>VarOutput2,...);

Step

Action

Open or create a new POU in Structured Text language.

NOTE: The procedure to create a POU is not detailed here. For more information on adding, declaring and calling POUs, refer to the related documentation.

Create the input and output variables and the instance required for the function block:

oInput variables are the input parameters required by the function block

oOutput variables receive the value returned by the function block

Use the general syntax in the POU ST Editor for the ST language of a Function Block. The general syntax is:

FunctionBlock_InstanceName(Input1:=VarInput1, Input2:=VarInput2,... Ouput1=>VarOutput1, Ouput2=>VarOutput2,...);

To illustrate the procedure, consider this example with the TON function block graphically presented below:

Function Block	Graphical Representation
TON

Function Block

Graphical Representation

TON

This table shows examples of a function block call in ST language:

Function Block	Representation in SoMachine POU ST Editor
TON

Function Block

Representation in SoMachine POU ST Editor

TON