ReadVal

<< Click to Display Table of Contents >>

Manual > Control Reference > Common to all controls > Common methods >

ReadVal

 

Get the tag value.

 

syntax

ReadVal(

         tagName,

         value

         [,dataSource = "clientcache"]

         )

 

Parameters

 

tagName

 

Type:

character

 

The tag name.

 

value

 

Type:

General purpose

 

The number to store the read value in. Only valid when the return value is TRUE.

 

dataSource

 

Type:

character

 

"clientcache" - Get the value from the client cache.

"servercache" - Get the value from the server cache.

"device" - Gets a value from a device.

 

 

Return Value

 

 

Type:

Boolean

 

FALSE - Failure. TRUE - Success.

 

Gets the value of a tag. This is almost the same as GetVal, with the following differences:

 

1) dataSource can be specified (GetVal is fixed to the client cache).

2) You can receive a return value indicating whether communication was successful or unsuccessful (especially with external tags).

 

ReadVal communicates one point at a time.

For example, for the data source "device", calling ReadVal multiple times will result in communication with the PLC each time, slowing down the overall performance.

In such cases, we recommend the ReadRefresh method.

 

 

hmtoggle_plus1Example

 


 

event OnInitialize()
{
this.AddTag("$D0");
}

event OnMouseUp(button)
{
var a;
if (!this.ReadVal ("$D0", a))
{
// Error handling
}
}

 

 

Supported

○

Script Action

Can be used in server script Ver2 actions

○

Browser script

Can be used in browser scripts

×

Calculation Expression Syntax

Can be used in expression syntax (e.g. bind syntax)

 

reference

 

AddTag

DelTag

ClearAllTag

GetVal

ReadVal

WriteVal

ReadRefresh

WriteRefresh

ReadRequest

ReadRequestRefresh

WriteRequest

WriteRequestRefresh