Tag Reference Open Display Example

How to have one display to share between many equipment, instead of having one display for each equipment.

How-to → Examples → Feature → UNS → Tag Reference Open Display Example

Overview

When you click any of the buttons, a display will open and a reference tag will be linked to the corresponding machine. This way, you can use a single display for all machines — instead of creating one display per machine — simply by changing the reference tag.

Data Model (UNS)

UserType: Machine

All machines share the same UserType, which defines the following process variables:

Tags

Simulated Values

Displays

MainPage

The home screen. Contains three instances of the MyButton symbol, one per machine.

When clicked, the button:

1. Sets @Tag.RefMachine.Link to the name of the selected machine tag
2. Sets @Tag.EquipNumber to the corresponding machine number
3. Opens the MachineStatus display

MachineStatus (Shared Display)

This is the single shared display used for all machines. All bindings reference RefMachine, never a specific machine tag directly.

Because all bindings go through RefMachine, the same display automatically reflects whichever machine is currently linked, no need for 3 different displays.

MyButton Symbol

The buttons on MainPage are instances of the MyButton symbol. Using a Symbol instead of a plain button means any visual or behavioral change made to the symbol definition is automatically applied to every instance across all displays.

Symbol Labels (Inputs)

Action Dynamic (on click)

The button executes three expressions on MouseLeftButtonDown:

Dynamic Label

The button label is built at runtime:

{#Equipment:(@Tag.Machine1).GetName().Replace("Tag.", "")}

This strips the Tag. prefix so the button displays a clean name like Machine1.

Navigation Header (Previous / Next)

The Header display includes Previous and Next buttons that are only visible when the MachineStatus display is open. They allow the operator to cycle through machines sequentially without returning to the main page.

An EquipNumber tag (Integer) drives the reference tag change.

Next Button Action

Previous Button Action

Both buttons use VisibilityDynamic with condition:

@Display.MachineStatus.IsOpened == true

So they only appear when the MachineStatus page is active.

Reference Tags — How They Work

A Reference tag is a special tag type that acts as a pointer to another tag of the same UserType. Instead of binding displays or actions directly to a specific machine tag, you bind them to the reference tag — and simply change what it points to at runtime.

In this demo, RefMachine is a Reference tag of type Machine. All displays bind through it, so switching which machine it points to is enough to update the entire screen.

The .Link Property

The .Link property is what you read or write to control which tag the reference is pointing to. It holds the target tag name as a string.

Usage Examples

Assigning directly from a tag name:

@Tag.RefMachine.Link = Tag.Machine1.GetName()

Building the link dynamically by concatenating a string with a tag value:

@Tag.RefMachine.Link = "Tag.Machine" + @Tag.EquipNumber.ToString()

Where This Pattern Appears in This Demo

In this section...