Cadence SKILL Language Introduction

Getting Started

Cadence® SKILL is a high-level, interactive programming language based on the popular artificial intelligence language,  Lisp . Because SKILL supports a more conventional C-like syntax, novice users can learn to use it quickly, and expert programmers can access the full power of the Lisp language. SKILL is as easy to use as a calculator as well as being a powerful programming language whose applications are virtually unlimited. SKILL brings you a functional interface to the underlying subsystems. SKILL lets you quickly and easily customize existing CAD applications and helps you develop new applications. SKILL has functions to access each Cadence tool using an application programming interface.

Cadence SKILL Language at a Glance

This section presents a quick look at various aspects of the SKILL programming language. These same subjects are discussed in greater detail in succeeding chapters. This section introduces new terms and takes a general look at the Cadence Framework environment. It explores SKILL data, function calls, variables and operators, then tells you how to solve some common problems. Although each application defines the details of its SKILL interface to that application, this document most often refers to the Cadence Design Framework II environment when giving examples.

SKILL is the command language of the Cadence environment. Whenever you use forms, menus, and bindkeys, the Cadence software triggers SKILL functions to complete your task. For example, in most cases SKILL functions can

• Open a design window

• Zoom in by a factor of 2

• Place an instance or a rectangle in a design

Other SKILL functions compute or retrieve data from the Cadence Framework environment or from designs. For example, SKILL functions can retrieve the bounding box of the current window or retrieve a list of all the shapes on a layer.

You can enter SKILL functions directly on a command line to bypass the graphic user interface.

Terms and Definitions

output

The destination of SKILL output can be an xterm screen, a design window, a file, or in many cases, the Command Interpreter Window (CIW).

CIW

Command Interpreter Window: The start-up working window for many Cadence applications, which contains an input line, an output area, a menu banner with commands to launch various tools, and prompts for general information. The output area of the CIW is the destination of many of the examples used in this manual.

SKILL interpreter

The SKILL interpreter executes SKILL programs within the Cadence environment. The interpreter translates a SKILL program's text source code into internal data structures, which it actively consults during the execution of the program.

compiler

A compiler translates source code into a target representation, which might be machine instructions or an intermediate instruction set.

evaluation

The process whereby the SKILL interpreter determines the value of a SKILL expression.

SKILL expression

An invocation of a SKILL function, often by means of an operator supplying required parameters.

SKILL function

A named, parameterizable body of one or more SKILL expressions. You can invoke any SKILL function from the command input line available in the application by using its name and providing appropriate parameters.

SKILL procedure

This term is used interchangeably with SKILL function.

Invoking a SKILL Function

Here are many ways to submit a SKILL function to the SKILL interpreter for evaluation. In many applications, whenever you use forms, menus, and bindkeys, the Cadence software triggers corresponding SKILL functions to complete your task. Normally, you do not need to be aware of SKILL functions or any syntax issues.

Bindkeys

A bindkey associates a SKILL function with a keyboard event. When you cause the keyboard event, the Cadence software sends the SKILL function to the SKILL interpreter for evaluation.

Forms

Some functions require you to provide data by filling out fields in a pop-up form.

Menus

When you choose an item in a menu, the system sends an associated SKILL function to the SKILL interpreter for evaluation.

CIW

You can directly enter a SKILL function into the CIW for immediate evaluation.

SKILL Process

You can launch a separate UNIX process that can submit SKILL functions directly to the SKILL interpreter.

You can submit a collection of SKILL functions for evaluation by loading a SKILL source code file.