Device DDT Instance

When adding a module to a rack, Control Expert software instantiates the associated device DDT structure. The main family of modules concerned by device DDT is the I/O modules family, some specific modules are also concerned. The device DDT name syntax is explained in the section on Device DDT Naming Rule.

Each module is associated with one implicit device DDT instance.

Implicit Device DDT instances are created by default on device insertion and refreshed automatically by the PLC. They contain the modules status, modules and channels health bits, values of the modules inputs, values of the modules outputs, etc.

NOTE: Optional explicit DDT types are proposed in the data editor to support status or command data used by explicit exchanges on a channel of I/O modules in a remote I/O drop. Explicit DDT instances are created manually by the user in the data editor and used as input or output parameter with the function block managing the explicit exchange.

Renaming a Device DDT

The following table describes a way to rename a module device DDT:

Step

Action

1

In the Project Browser, double-click the module that contains the device DDT to rename.

2

In the module window, select the Device DDT tab.

3

Select the module (not the channel).

4

Modify the device DDT name.

NOTE: The total name length is limited to 32 characters.
NOTE: A name needs to be unique in an application.

5

Validate the name changes in the advice window. This advice window appears when selecting another tab or view.

Copying and Pasting a Module

During a module copy/paste action, the pasted module respects the default naming rule linked to its topological location.

Moving a Module

Moving a module does not modify its name.

If the same module type is inserted in the slot freed by the module shifting, the new inserted module should get the same topological name. In order to keep the naming uniqueness, _rrrrrr is added at the end of the string (rrrrrr being a random character series).

Replacing a Hot Standby CPU

Replacing a Hot Standby CPU does not modify the device DDT name of the CPU.

Checking the Device DDT Owner

When a module is moved or a Device DDT is renamed, it may be difficult to locate the module in the architecture. This information is provided in the Owner column of the Data Editor. Displayed columns are configured as needed.

Creating a Device DDT Instance

Perform the following steps to create a Device DDT instance:

Step

Action

1

Select the Variables tab in the data editor.

2

Double-click the empty cell Name (marked with an arrow) and enter the name of the instance.

3
Double-click the corresponding Type field and click the following button:

Results: The Variable Type Selection dialog appears.

4

In the Libraries/Families area, display the <Libset vx.y> index.

Where x.y indicates the Control Expert software version.

5

Select the family ( I/O Management for example) and the corresponding Device DDT type.

6

Confirm with OK.

Example: Instance ANA_OUT of type T_U_ANA_STD_OUT_8:

Linking a Device DDT Instance to a Module

Use the following procedure:

Step

Action

1

Create a Device DDT as explained previously.

2

In the Project Browser, double-click the module to be associated to the created device DDT.

NOTE: The created device DDT can only be linked to a module of the same type. For example, an 8 analog input module can only be linked to an 8 analog input device DDT.

3

In the module window, select the Device DDT tab.

4

Select the module (not the channel).

5

In the Implicit device DDT > Name : list, select the name of the device DDT created (instead of the current name).

6

Validate the name changes in the advice window. This advice window appears when selecting another tab or view.

NOTE: Once a module is linked to a new device DDT, the variables that were linked to former device DDT name do not address the module anymore.

7

The previously created Device DDT instance is now linked to the module. It is displayed as follows in the data editor:
NOTE: A variable linked to a module shows a lock in front of its name in the data editor.