TagDirectWriteString Function

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Writes a string value directly to an address in a data source. Uses the DirectWriteString Tag Command.

Functions and Function Blocks

The TagDirectWriteString Function is intended for use in an Operator Action. Operator Actions run in response to user input gestures in the Operator Interface. In an Operator Action, code execution is suspended until the function completes.

To write a value from a Program Tag, running on the SCADA Server, use the TagDirectWriteStringFB Function Block.


Informal Syntax:

TagDirectWriteString( TagName, DataAddress, Value )

Formal Syntax:

        Value:=Expression )


Parameter Type Description
TagName ANY_STRING The full name of the tag that represents the data source.
DataAddress ANY_STRING The "Address" of the data within the data source. See Data Address Format to understand how to set the "Address".
Value ANY_STRING The value to write to the data source.

Return Value



The TagDirectWriteString Function sends the DirectWriteString Tag Command to the database tag.


Sends the DirectWriteString Tag Command to the tag "MQTT Connection" to write a string value to address "TopicPath/ControlItem".

TagDirectWriteString( "MQTT Connection", "TopicPath/ControlItem", "{ $"State$" : $"On$" }" );

Further Information

DirectWriteString Tag Command

To learn about the DirectWriteString Tag Command.

TagDirectWriteStringFB Function Block

To learn how to write a bit directly to a data source from a Program Tag.

Operator Actions

To learn where you can use this function.

Structured Text Function Call

To learn about calling a function from IEC 61131-3 structured text.

IEC 61131-3 Expressions

To learn about the different types of expression to use as function parameters.


For the meaning of terms used in Fernhill SCADA.