Access types define the specific methods by which values are read and written for each specific data point, such as a polling rate, if a read is performed on startup, and if unsolicited input is accepted.

There are 3 predefined Access Types that you can use (Read, Write, and ReadWrite), or you can create your own.

Creating a New AccessType

To create or edit an AccessType:

  • Go to Edit > Devices > AccessTypes.
  • To Edit an existing type, double-click on a field and configure it as desired.
  • To Create a new type, click on the CreateNew button.


Configuring AccessType as OnDisplayOrServer

On the dialog window, you need to configure the ReadEnable field to OnDisplayOrServer.

This property is enough for the Reading portion of the communication. You can also enable Writing Events by selection the WriteEventEnable checkbox.


Access Type Characteristics

The OnDisplayOrServer Access Type is a great tool for projects that have a large amount of Communication Points but do not require the data to be constantly updated for all of them.

It can help computers that lack computational power to handle a huge volume of data exchange while also maintaining other modules (Scripts, Alarms, etc) at the same time.

In these situations, an OnDisplayOrServer Access Type can be beneficial to the Project's performance.

The OnDisplayOrServer Access Type operation process can be divided into two aspects:

  • OnDisplay
  • OnServer

ONLY when and while ANY one of these are matched, the Communication Points with this AccessType can Read/Write data.

On Display

The OnDisplay part means that your Communication Point will only begin Reading/Writing when the Project display that contains these tags is actually open.

To illustrate, lets say we have a project with two displays, one for LineA and the other for LineB. Each displays has its own specific Tags added to it (Tag.LineAProduct1..., Tag.LineBP roduct1...)

When the Project is running, there is no need to send/receive data for all Tags in the PLC. The Project only needs to send/receive data for the ones that are in the display that is currently opened on the Visualizer.

So, when LineA display is open, only LineA tags will comunicate. The same goes for LineB.

Or Server

The OrServer or OPCServer means that if your Project is running as an OPC Server the AccessType will behave as if its ReadEnable property is set to Always.

If you have the tags on the server-side as Script Tasks, Classes, Expression, Alarm Items, etc. You need to create a new AccessType specific for them with the ReadEnable option in Always.


  • No labels