Validation Functions

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Fernhill SCADA supports these validation functions defined by the IEC 61131-3 standard:

FunctionParameter TypeDescription
IS_VALID ANY_REAL Return TRUE if the parameter is a valid REAL number.
IS_VALID_BCD ANY_BIT Return TRUE if the parameter is valid BCD.

Fernhill SCADA supports these functions as an extension to the IEC 61131-3 standard:

Function Parameter Type Description
IS_DEFINED ANY Returns TRUE if the parameter is defined.


The Validation functions check if the input parameter contains a valid value.

The function IS_VALID() checks the input parameter represents a valid floating point number. The function returns FALSE, if the input parameter is not a number (NaN) or infinite.

The function IS_VALID_BCD() checks the input parameter is valid BCD.

The function IS_DEFINED() checks the input parameter is a valid value. This function is useful to check whether a tag reference is valid. For example, the expression IS_DEFINED( %"Tag Name" ) will return:

Standards Compliance

IEC 61131-3 Third Edition: Table 39.

Further Information

Generic Data Types

To learn about generic data types such as ANY_INT, ANY_NUM, ANY_MAGNITUDE.

Time Functions

To learn about arithmetic operations on date and time types.

Common Elements

To learn about other language Common Elements.


For the meaning of terms used in Fernhill SCADA.