Analog Control Tag Type Properties: I/O Tab
In the I/O Tab, you will find the properties used to identify and establish a connection to the communication driver tag being used to exchange data with your physical I/O device (e.g. PLC or RTU), or to the polling driver responsible for determining the order and rate at which data polls will occur.
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Select the communication driver tag to which data will be written.
The tag button to the right of the field opens the tag browser, from which you can either select an existing communication driver tag or add a new one. The X button will clear the field. Right-clicking on a tag in the field will open a dialog from which you can the driver`s properties.
Provide the address within I/O device to which this tag is to write data. This value must match the configuration of your PLC or RTU hardware.
The addressing system for each of the drivers that come with VTS is provided in the Communication Driver Tags section of this guide.
Provide units of measure that the input data represents. Possible values for this field include "rpm" "degrees C", "%", etc.
[Optional] While analog control tags usually take their value from an operator-controlled drawing object, the Data Source field provides the option of configuring this tag to accept a value from another tag or expression instead.
The value from the Data Source can be written to the I/O device, or it can be used to simply update the drawing method display. See the following topics: Write output when Data Source Changes and Use Data Source for display only.
If you have selected a data source that is configured to write output, and have also drawn the tag as an object that operators can use to set values, then both can write to the I/O device. The value written will be whichever was most recently changed.
Write output when Data Source changes
When selected, the value supplied by the data source tag or expression will be written to the I/O device and will also be used to set this tag’s value. Selecting this option automatically de-selects the “Use Data Source for display only” option.
Use Data Source for display only
When selected, the value supplied by the data source tag or expression will not be written to the I/O device, but will be used to set this tag’s value. Selecting this option automatically de-selects the “Write output when Data Source changes” option.