2.1.5. Device Data Item Device ID and Address  

About this task

The Data Item dialog box Device tab provides the flexibility to use the class template for different object requirements.

  • Device ID field.
  • Addressing.

Device ID Field

A Data Item dialog box for a device does not include a Device ID field.

The device is assigned to the object in the Object dialog box.

Important: Each object can support only one device.

The device is included, as follows, for instantiation.

A Class: Data item configuration
B Object: Object defined.
C Instantiation: Point properties result.
  1. Class: Data Item Configuration

A device cannot be entered for a data item.

There is no Device ID field in the Data Item dialog box.

Example

A device Data Item dialog box named VLVBP has no Device ID field.

  1. Object: Object Defined

A Device ID is entered at the object level.

Object Created

Class objects are created from the class.

Example

A class object created from the class TANKS is named: STATION01.

Attribute Value Assigned

A Device ID must be entered in the Object dialog box.

Note: If you plan to create device data items and objects already exist, enter a device ID in each Object dialog box before you create the device data items. If you do not, you will not be able to apply the changes to the class. You can change the device at anytime.

Example

The STATION01 Object dialog box has TRIPLEXDEV entered in the Device ID field.

  1. Instantiation: Point Properties Result

A Device ID field, which is read-only in the Point Properties dialog box, displays the device ID that is assigned to the object.

Example

The Device ID read-only field in the STATION01.VLVBP Point Properties dialog box displays the TRIPLEXDEV device.

Address field

An address does not have to be entered in a Data Item dialog box for a device data item.

An address is instantiated with an object as follows.

A Class: Data item configuration
B Object: Object created.
C Instantiation: Point properties result.
  1. Class: Data Item Configuration

An address does not have to be entered in the Address field for a device data item but if an address is entered:

* It overrides an address entry in the Object dialog box.   

* It is applied to the instantiated point for every object  {$OBJECT}.<point ID> in the class.

* Do not configure the $ADDRESS_ADJ data item.  A Device Base address should only be specified at Class level attribute or Object level attribute when instantiated or modified at Object properties.

Example

The Address field in a device Data Item dialog box for a device data item named VLVBP has no entered address.

  1. Object: Object Configuration

A different base address can be entered for each object in the class.

Object Created

Class objects are created from the class.

Example

A class object created from the class TANKS is named: STATION01.

Attribute Value Assigned

An address is entered in the Address field in the Object dialog box.

Example

STATION01 is assigned the %5R address.

  1. Instantiation: Point Properties Result

The read-only Address field in the instantiated point's Point Properties dialog box displays, in the following priority, the address entered in the:

Procedure

  1. Data Item dialog box.
  2. Object dialog box.

    Example

    The read-only Address field in the STATION01.VLVBP Point Properties dialog box displays the %5R address entered in the Object dialog box.

    Note: If a different address, e.g. %8R was entered in the STATION01.VLVBP Data Item dialog box, that address would display in the Point Properties dialog box.

    The Address field for other STATION01 object points display %5R or addresses entered in their Data item dialog box.