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Further Benefits of Top-Down Design

Principles of Top-Down Mixed-Signal Design

In this way, the designer uses his or her deep knowledge of the block and its perfor- mance to develop the model.

For more complex block like a phase-locked loop (PLL) or a clock-and-data recovery (CDR) circuits the behavioral models are often created by the system designer or by an assigned modeling engineer. Such models tend to call for sophisticated and rather spe- cialized modeling skills and generally require substantial effort expended throughout the duration of the project.

The top-level designer would take responsibility for developing the behavioral models for overall system test bench, perhaps with the help of the system designer or modeling engineers.

7 Further Benefits of Top-Down Design

Besides the benefits described in the previous two sections, a rigorous top-down design methodology addresses all of the various needs and issues described in Sections 1-2.6, which includes the following.


Improves Communications Between Engineers

Communications between the designers is improved in two substantial ways. First, the use of a shared high-level model of the system that everyone verifies their designs in eliminates most of the miscommunication that occurs when following either bottom-up of primitive top-down design processes. In addition, the executable specifications and plans (models and scripts) are more specific and less ambiguous, and considerably reduce the time spent writing and reading formal specifications, providing a more effi- cient and effective replacement.


Improves Productivity

The improved productivity that results with a rigorous top-down design process is due mainly to the elimination of mistakes and respins. A more formal, less error-prone design process with better communication between engineers means that less time is spent making and recovering from mistakes, and more time is spent on productive design tasks.


Improves Ability to Handle Complex Designs

The ability of a design team following rigorous top-down design methodology to handle more complex designs follows from the better system exploration and from the increases understanding of the design that comes from it, and from the improved com- munications. In addition, the use of mixed-level simulation dramatically improves the teams ability to verify complex circuits.

7.4 Allows Parallel Execution of Design Tasks

Reducing time-to-market is an important way in which design teams can increase their chance of success and the returns of their products. Part of the reduction in time-to-mar-

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