The I/O String Data Point Tag
maps a variable length string to an external data source.
The I/O String Data Point Tag supports the configuration properties of the String Data Point Tag plus these properties:
Property | Type | Version | Description |
---|---|---|---|
AllowControls | BOOL | 3.12 | Whether Fernhill SCADA can send controls from this tag to the data source. |
IODataSource | Reference | 3.12 | A reference to another tag that provides the external data for the tag. |
IOItemName | WSTRING | 3.12 | The data item within the external data source. |
OutOfService | BOOL | 3.92 | Whether retrieval of data from the external data source is suspended for this data point tag. |
The AllowControls property controls access to the WriteValue Tag Command.
When AllowControls is FALSE, access to the WriteValue Tag Command is blocked. This prevents any user, or program, sending control requests to the data source from this tag. The default value is FALSE to follow security best practice of deny by default.
Even when AllowControls is TRUE, an operator requires the Write User Privilege to send controls to the data source.
For an operator to send a control to the data source, both of these conditions must be true:
The IODataSource and IOItemName properties define which data item the I/O String Data Point Tag is associated with:
To configure these properties:
Note: The format of the IOItemName property depends on the type of data source chosen.
To understand how the IOItemName property is formatted, see Data Address Format.
Use the OutOfService property to suspend retrieval of data from the external data source.
For normal operation, OutOfService should be set to False. If a data source is providing faulty data, it might be appropriate to set OutOfService to True.
The I/O String Data Point Tag supports the data properties of the String Data Point Tag.
The I/O String Data Point Tag supports tag commands of the String Data Point Tag plus these tag commands:
Tag Command | Version | Description |
---|---|---|
WriteValue | 3.12 | Writes a new value to the data source via the I/O tag. |
The I/O String Data Point Tag builds on the features of these tag types:
To learn about properties common to all String Tags.
To learn about the Core Data Driver.
For the meaning of terms used in Fernhill SCADA.