Overview
The Device AccessType defines the defines the rules for reading and/or writing values for Device Point. Each Point is associated with one AccessType.
Settings include among others: polling rate, read on startup, and if is enable to writing.
On this page:
Creating an AccessType
To create and configure an AccessType, follow these steps:
- Access Devices → AccessTypes.
- Click on the plus icon.
- Fill all the property fields with your desired configuration (see the table below for more details about each option).
- Click Ok.
AccessTypes properties
The following table describes each configuration property when creating an AccessType:
Field | Description |
|---|---|
Name | Name of this AccessType. |
Read | |
ReadPolling | Enables read polling. |
ReadPollingRate | Defines how often the address value is retrieved. |
ReadTrigger | Enter an object property that tells the system when to read the value. |
OnStartup | When selected, the system reads the value on startup. |
Write | |
WriteEvents | Enables the writing of values to the PLC. |
WriteEvent | Defines when is the value written. |
WriteTrigger | Enter an object property that tells the system when to write the value. |
Settings | |
AcceptUnsolicited | If enabled, the system accepts values from the PLC, even if the polling time has not yet elapsed. |
UseStaticBlocks | Enables the use of the block command field. |
BlockCommand | A definition for each block that will be created. Check the driver documentation to see if the specific driver uses this field and the valid values. |
Description | Description of the access type. |
OnDisplayOrServer setting
The OnDisplayOrServer AccessType is an excellent tool for solutions with many communication points but only requires data updates for some of them. It can help computers without the computational power to handle massive data exchange while maintaining other modules active. The OnDisplayOrServer operation process is divided into two aspects:
- On Display: On Display means that your DevicePoint will only begin reading or writing when the solution's display containing these tags is open.
- Let us imagine a project with two displays, one for Line A and another for Line B. Each display has its specific Tags added to it. When the Project is running, there is no need to send or receive data for all tags in the PLC. The solution only needs to send or receive data for the opened displays of the visualizer. So, when the Line A display is open, only Line A tags will communicate. The same goes for LineB.
- On Server: On Server or OPCServer means that if your solution runs as an OPC Server, the Access Type will behave as if its Read Enable property is set to Always.
- Suppose you have the tags on the server side as ScriptTasks, Classes, Expression, or AlarmItems. In that case, you must create a new AccessType specific for them with the Read Enable option in Always.
Configuring an AccessType as OnDisplayOrServer
To configure an Access type as On Display Or Server, follow these steps:
- Access Devices → AccessTypes.
- Click on the plus icon.
- On the ReadPolling property, choose OnDisplayOrServer. This property is enough for the Reading portion of the communication.
- Check the WriteEvents box to Enable Writing Events.
Only when these options are met can the DevicePoints with this AccessType read/write data.
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