Linking Hardware Resources to Hardware Operators

As schemas grow in size and complexity, it may become cumbersome to determine which module's hardware resources have been linked to schema operators. It is often useful to be able to view a list of all module hardware resources that are referenced by associated schema documents. You can view such a list by clicking the right mouse button on the desired module and selecting the Hardware Connection Window item from the drop-down menu (note that this menu option is only available in modules that have user-accessible hardware resources).Figure 4.13 shows the Hardware Connections dialog for the PCM-1 module of the hardware interface file shown in Figure 2.4. You can click on any module in the left column to view its hardware connection listMention help when coded. All of the available hardware resources for the selected module are displayed in the rightmost list control, and the list of linked resources is displayed in the center window. The name of each operator (and the schema path and module it is associated with) is displayed under the resource name or channel number. (Typically a hardware resource is connected to a single operator but it could be connected to multiple operators.)

Figure 4.13. Module Hardware Connection Window Dialog.

You can also create a new link between resource and a schema operator by double-clicking on the unconnected resource in the rightmost list box of the Hardware Connections dialog (Figure 4.13). Note that the previous section described how to link a hardware operator in a schema to a hardware resource in a module. This section describes how to link a hardware resource in a module to an operator in a schema. (The link between operator and resource is the same regardless of how it is formed. However, in some instances it may be convenient to first select the operator and then the resource. In other cases, selecting the resource first and then the operator may be the preferred approach.)

Figure 4.14. Connect Hardware Resource To Operator Dialog.

Double-clicking on a resource in the rightmost list box of the Hardware Connections dialog activates the Connect Operator To Hardware dialog shown in Figure 4.14. The dialog shows a list of unconnected generic hardware operators that are available in the node for connection to the selected hardware resource. To create a resource/operator link, select the available operator and click the OK button.

 
The links between schema operators and module hardware resources are stored in the hardware interface file. (The hardware interface file references linked operators by their user-defined Object Name property.) Because schema documents and hardware interface documents are stored separately, some of these hardware associations may be inadvertently broken. This could occur for example, if a schema document is edited while a hardware interface file that references that schema is not concurrently open. Consider a Design Pad G4 session where the Figure1PCM.scm schema of Figure 2.5 is opened for editing independently of the Figure1.hwi hardware interface document of Figure 2.4. (such that the schema background color is white). Suppose that the Object Name property of the Analog Input operator is changed from "SAM RTD" to "SAM TEMP". Then, when the Figure1.hwi document is opened, it will still reference a connection to an operator named "SAM RTD" that no longer exists. Note that if the Object Name property of the schema operator is changed while the hardware interface file is also open (such that the schema background color is non-white) the link is automatically updated.

The Clean Unlinked Connections button in the Hardware Connection Window of Figure 4.13dialog will search through the list of module hardware associations and remove any link referencing an operator that can no longer be found.