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Logic kỹ thuật số thử nghiệm và mô phỏng P2

Simulation is an imitative process. It is used to study relationships between parameters that interact in a system. In some cases it may point out errors that cause a design to respond incorrectly. In other cases it permits optimization of a design for maximum performance or economy of operation or construction. In still other situations, the system may be so complex that simulation is the only way that variables affecting the design, and their interaction with each other, can be controlled and studied. In order to imitate the behavior of a product or system, simulation employs models. A model is. | CHAPTER 2 Simulation 2.1 INTRODUCTION Simulation is an imitative process. It is used to study relationships between parameters that interact in a system. In some cases it may point out errors that cause a design to respond incorrectly. In other cases it permits optimization of a design for maximum performance or economy of operation or construction. In still other situations the system may be so complex that simulation is the only way that variables affecting the design and their interaction with each other can be controlled and studied. In order to imitate the behavior of a product or system simulation employs models. A model is an imperfect replica. It must contain enough information to accurately represent the behavior of the variables of interest in the process or system being studied but must not be so complex as to obscure details of the variables and their relationships or so intricate that its cost approaches that of simply building the device or system to be studied. This chapter will focus on methods used to simulate digital logic circuits in order to predict their behavior in the presence of various stimuli and environmental factors. Note that the accuracy of the prediction of circuit response depends on the accuracy and level of detail of the circuit model provided to the simulator. In future chapters we will examine fault simulation and other methods for verifying correctness of designs and correctness of the fabricated product. Much can be learned by comparing and contrasting methodologies used in simulation and fault simulation with those used in design verification. In fact as circuits get larger and more complex the arguments for integrating design and test activities become more compelling. To the extent that the design effort can be leveraged in the manufacturing test development task the overall development cost for design and test can be reduced. 2.2 BACKGROUND Early designers of digital logic implemented their circuits on printed circuit .