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Adding Tags

NOTE

If you experience difficulty communicating with your PLC after adding tags, as a first step, ensure you have used the correct tag syntax. Using an incorrect syntax for a tag means that the WebPort will not be able to read the tag on the PLC.

Tags are data elements on a Data I/O device, such as a programmable logic controller. Legacy controllers and Modbus-based controllers have numeric addressing requirements. Later controllers may have logical name tags. Most interaction with these devices uses tags. Alarms, events, actions, reports, emulators, and datalogs all provide tag selection options. Restricted characters that may not be used in tag names are: ^\{};<>%'"., &. When creating a tag, you may designate the tag to be read-only. This means the tag value cannot be changed by the user. When a tag is referenced by an alarm or by a Datalog, an X appears in the relevant column. Tag addresses (or IDs) frequently combine device type and the tag name. Example: PumpController2.Level3

To add a tag:

  1. From the Configuration Work Area, select the following icon: This is a picture of the dialog. The Devices dialog appears: This is a picture of the dialog.
  2. Click the following Tags dialog icon: This is a picture of the dialog.

    The Tag Properties dialog appears. (Default dialog shows no device information):

    This is a picture of the dialog.
  3. From the Tags dialog, view or specify the following options:
    • Tag Name. Enter name of tag. Example: Local:1:ICh0Data
    • Description. Enter tag description. Example: Tag block for sensing
    • Data Type. Select data type for tag. If the device protocol is PPI, the Data Type field does not appear. See also Defining Tag Data Types
    • Address. Enter address of tag. Additional Tag entry examples:
    • Unit. Enter engineering units associated with Tag. Example: Degrees Centigrade.
    • Read Only. Specify whether or not tag data may be modified. When selected, you cannot modify the tag Value field. (The address and unit can be modified even if it is read only.)
    • Scaling. Specifies the scaling multiplier or divisor applied to the selected tag. You cannot scale strings and Booleans. You specify whether to multiply or divide the tag, and provide an additional value (REAL or INT) by which to multiply or divide the tag. The value for the tag that is displayed is the value that is also visible in RSLogix. Example. If you have a tag value 1.29446, and you specify a divisor of 2, the scaled value is 0.64723. If you specify a multiplier of 2, the scaled value is 2.58892. You cannot enter a scaling value of zero (0). The operation is carried out on the tag value as the value is written to the WebPort database. Any place that the tag is referenced in the software, the scaled value is returned, not the original value. Display areas include Live Data, Charting, and Datalogs. It will also affect the evaluation of alarms. You may also specify an offset:
      • Offset. The offset is applied such that: This is a picture of the dialog.

        y = mx+b

        Where:

        m is the slope

        x is the raw tag value

        b is the offset

    • Use Lookup Table. Configures a tag so that a user-defined lookup table is used to produce a value. When you select this option, you are prompted to enter a list of values and messages. The translation of tag values to messages is done as the tag is written to the WebPort database. Any place that the tag is referenced in the software, the string is returned, not the value. Display areas include Live Data, Charting (Message Type indicator), and Datalogs. Example: 0=Motor ON; 1=Motor OFF; 2=Motor Too Slow; 3=Motor Too Fast
      • When you choose to use a lookup table, the following list appears: This is a picture of the dialog. Enter your values and descriptions.
  4. Submit. Saves changes on WebPort and exits.
  5. Cancel. Exits without saving changes on WebPort.

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