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Background documentationTag Definition Tab

 

On this tab, you enter the tags for the devices that you want to monitor. The tags are displayed in a structure. You can also create a namespace hierarchy for the tags.

The tab is divided into two areas:

The structure or namespace hierarchy of the selected tags is displayed in the left screen area. This area is empty at first. The structure is only displayed once tags have been entered.

The input fields for entering tags are offered in the right screen area.

Procedure

  1. To enter the first tag, you enter details for the tag as follows:

    Field

    Description

    Access Path

    You enter the access path for the tag here. The symbol . is used as a separator within the path. The depth of the path can be freely defined.

    Description

    You can enter a description of your choice for the tag here.

    Update Rate

    Here you define the update rate for the selected tag in milliseconds.

    The update rate specifies the minimum time that needs to have passed between two consecutive query operations (reading and sending the value). Since the tag is queried using the polling method (see: Polling), it is important to reduce the amount of communication between the Modbus devices. Therefore, it makes sense to define a larger update rate.

    Note Note

    The value that you enter here is used together with the minimum update rate that you specify on the Modbus Agent tab to define the actual update rate for sending values from the Modbus source to PCo. (See also: Determining the Update Rate.)

    End of the note.

    Deadband

    Limit value for filtering out measurement values. Here you can enter a percentage to define the bandwidth in which the value of a tag must at least change before the Modbus device reports the value to PCo as changed.

    Note Note

    The defined percentage can only be used for numerical tags.

    End of the note.

    If you enter 0%, each value change of a tag triggers a notification message.

    Type

    The following types of tags are supported:

    • Boolean

    • Boolean [ ]

    • Byte

    • Byte [ ]

    • Double

    • Double [ ]

    • Int16

    • Int16 [ ]

    • Int32

    • Int32 [ ]

    • Int64

    • Int64 [ ]

    • Single

    • Single [ ]

    • String

    Note Note

    Tags of the type Boolean cannot be defined in files. Tags of the type byte can only be defined in output coils or input contacts.

    End of the note.

    Unit ID

    ID of the device or the PLC for which you want to define the tag.

    Here you enter the unit ID of the device that you defined previously on the Slave Unit tab.

    Address

    Here you enter the address of the selected tag.

    The following address overview indicates which addresses you need to specify for a specific tag (the file number is 0 in these cases):

    • Output coil

      000000 ... 065535 (or H00000...H0FFFF)

    • Input contact

      100000 … 165535 (or H10000 … H1FFFF)

    • Input register

      300000 … 365535 (or H30000 … H3FFFF)

    • Holding register

      400000 … 465535 (or H40000 … H4FFFF)

    To specify the address in a file, use the interval 000000 … 065535 (or H0000 … H0FFFF).

    To define a tag of the type Boolean in an input address bit or holding address bit, you need to specify a bit offset.

    Example Example

    The following addresses are examples of Boolean tags:

    400001.0, 401111.15, 300001.7, and so on.

    End of the example.

    The bit offset must be between 0 and 15 (only in conjunction with input and holding register addresses.

    File Number

    Specifies the file number of the tag. You use 0 as the file number if the selected tag has been defined in output coils, input contacts, input registers, or holding registers.

    Size

    Specifies the size of the tag in the address space.

    If it is a bit address (output coil or input contact), you enter the size of the tag here in bits.

    If the address is an input register, holding register, or a file, the number of the 16-bit register is specified here.

    The system sets the size automatically if the selected tag is not an array or a string.

  2. If you want to enter another tag, choose the Add New Modbus Tag pushbutton.

  3. If you want to change an existing tag, select the tag in the structure and choose the Edit Modbus Tag pushbutton.

  4. If you want to delete a tag, select the tag in the structure and choose the Delete Modbus Tag pushbutton.

  5. You can use the Export pushbutton, to export the configuration of the tags that you have entered here on the Tag Definition tab and store it as a CSV file so that this tag configuration can be used for another Modbus source system. (See: Importing or Exporting Modbus Tags.)

  6. You can use the Import pushbutton to import an existing tag configuration. (See: Importing or Exporting Modbus Tags.)