The tag value is retrieved from the browser's client cache. GetVal returns the tag value as the return value. As long as the tag name is correct, the return value is guaranteed to be valid.

If there is an error in communication with the PLC or server for an external tag, the last successfully retrieved value will be returned.

To know more about the communication status, refer to the quality flag (GOOD/BAD/UNCERTAIN). The quality flag can be obtained using the following method.

For example, use the quality flag if you want to switch processing depending on the communication status.

For external tags, if no communication has been made yet, "N/A" (UNCERTAIN) will be returned.

Immediately after AddTag, no communication has been performed yet, so the state will be UNCERTAIN for a few seconds. To perform communication immediately after AddTag, call the ReadRefresh method immediately after AddTag.

var vVal = this.GetVal("U01.F01.T01");

::IsQualityGood(vVal); // Communication is going well (GOOD), TRUE
::IsQualityBad(vVal); // Communication is unsuccessful (BAD), TRUE
::IsQualityUncertain(vVal); // Communication has never taken place (UNCERTAIN), TRUE
::GetQuality(vVal); //"GOOD" or "BAD" or "UNCERTAIN"

GetVal can be used on objects for which tags have been registered using AddTag.

Example 1) When calling GetVal in the script of a registered control

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

event OnMouseUp(button)
{
 this.Text = this.GetVal("$D0");
}

Example 2) Registering tags in a form and calling methods from each control

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

// Event for each control 
event OnMouseUp(button)
{
this.Text = parent.GetVal("$D0");
}

You can also specify multiple tag names as a string array as follows:

If multiple tags are specified, the returned value will also be an array. In the following example, the value of "$D0" will be stored in a[0], and the value of "$D1" will be stored in a[1].

var a = this.GetVal( c("$D0","$D1","$D2","$D3","$D4") );

In addition, the server can set tags as array tags as follows: For example, D0000 to D9999 of the PLC device can be defined as one array tag.

When getting the value of an array tag with GetVal, specify only one tag name, like this: a = this.GetVal("TAG01");

In this case, the return value will be an array. For example, the value D0000 will be stored in a[0], the value D0001 in a[1], and the value D1000 in a[1000].