Calculated Double Word Data Tag

Introduction

The Calculated Double Word Data Tag Double Word Tag Icon maps a 32-bit unsigned integer to the result of a calculation. The calculation can run:

Configuration Properties

The Calculated Double Word Data Tag supports the configuration properties of the Double Word Data Tag plus these properties:

Property Type Version Description
UpdateInterval TIME 1.3 The interval between each calculation. A value of zero (T#0s) disables periodic calculation. See Interval and Offset for information on how timed activities are scheduled.
UpdateOffset TIME 1.3 The offset added to the UpdateInterval to get the actual update time. See Interval and Offset for information on how timed activities are scheduled.
InstructionLimit UDINT 1.3 The maximum number of instructions to execute.

The Calculated Double Word Data Tag evaluates a Calculation at the periodic interval defined by the UpdateInterval and UpdateOffset properties. The result of the calculation is written to the tag. Setting UpdateInterval to T#0s disables periodic calculation.

Calculation

The value of the Calculated Double Word tag is defined using an IEC 61131-3 Expression.

To edit the calculation, right-click the tag in the Tag Window, and then click Edit Calculation. The calculation is edited using a Program Code Editor.

Dynamic Properties

The Calculated Double Word Data Tag supports the dynamic properties of the Double Word Data Tag plus these properties.

PropertyTypeDescription
ExecErrorCode DINT The result of the execution. A zero value shows success. A non-zero value shows an error occurred.
ExecErrorLocation DWORD The address of the instruction that caused the error. Zero if there was no error.
ExecInstructionCount UDINT The number of instructions processed by the program during the latest execution.
ErrorMessage WSTRING The execution error message. An empty string shows no error.
UpdateTimer TimerStatus The status of the calculation update timer.

Tag Commands

The Calculated Double Word Data Tag supports tag commands of the Double Word Data Tag plus these tag commands:

Tag Command Version Description
Run 1.3 Evaluates the expression and writes the resulting value to the tag.

Relationships to Other Tag Types

The Calculated Double Word Data Tag builds on the features of these tag types:

Further Information

Interval and Offset

To learn how activities are scheduled using Interval and Offset.

Expressions

To learn about the expressions that can used in the Calculation property.

Double Word Data Tag

To learn about properties common to all Double Word Tags.

Core Data Driver

To learn about the Core Driver.

Glossary

For the meaning of terms used in Fernhill SCADA.