Mixed circuit logic level simulation

The design of a data or signal processing system is partitioned into analogue and digital modules according to the level of signal abstraction required. Interaction between analogue and digital modules of the circuit makes independent simulation of the modules less useful particularly when signals pass round closed loops incorporating both analogue and digital modules. Circuit level simulation of the whole system while accurate, is too costly and anyway circuit-level characterisation of digital modules is not always available. These considerations drive the development of mixed-mode simulators for logic level simulation, while less precise, in three to four orders of magnitude faster than circuit level simulation. The integration of a circuit simulator and a logic simulator into the same package, however, requires attention to details of interfacing, both of signals at different levels of abstraction and of time flow in the two simulators. These issues are the substance of this presentation