Expression Editor

The Expression Editor enables users to enter Link Expressions quickly and easily. Expressions are made up of Outputs, Operators and Constants. A tab is provided for each of these so the user can select a value by clicking on the appropriate item. Expression terms can also be entered from the keyboard, as any standard editor.

A UML Link is a connection between UMLObjects. In UML2HDL a Link is represented by an expression. In general, a link is assigned to each UMLObject Input. A Link expression can be as simple as a single UMLOutput, which represents a connection from the UMLOutput to the UMLInput. A Link expression can also include other UMLOutputs or Constants interspersed with Operators, for more complex connections.

In UML2HDL Expressions define the following:

To open Expression Editor, Select an Object for Editing, then select one of the above items in the Properties editor, and click the  button .

Fig.11 Working with Edit Expression dialog

Expressions are entered in the selected HDL which is displayed in the top toolbar. Care must be used when entering expressions since they must be syntactically correct in order for the generated HDL to compile without errors. If there are errors in the generated HDL, it is generally because an expression was incorrect.

The Expression Editor checks basic syntax, and indicates wheter the expression is syntactically correct. It is important that the expression is error free before it is entered by clicking OK.