The Mixed-Mode Interface
A major issue in all mixed-mode simulators is the problem of interfacing of two or more simulation modes. This chapter describes the modeling problems of these interfaces and possible solutions. Of course, this problem arises only when elements from different modes of simulation are connected at a common node. There are two possible directions of signal conversion: one from the lower level of simulation (more detailed) to the higher level of simulation (less detailed), and a second going in the opposite direction. For example, logic simulation and electrical simulation require signal conversions from logic to electrical simulation and from electrical to logic simulation. Typically, it is easier to translate a signal from a lower level of simulation to a higher level since the conversion involves removing unnecessary details from the signal. Signal conversions from a higher to a lower level are more difficult since the information required at the lower level is often unavailable at the higher level. In particular, it is the conversion of signals from the logic domain to the electrical domain that is most troublesome. Both types of signal conversions are described in this chapter. A number of examples are used to illustrate potential problems of the various interface models in use today.
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