Edisim and Edicap: Graphical Simulator Interfaces

Edisim and Edicap are new CAD tools that greatly simplify the use of simulation in LSI design. Unlike previous simulator systems which require the user to type in commands textually, the edisim/edicap user works directly from the chip layout displayed on a color monitor. Input nodes are identified merely by pointing to them. This eliminates the problem of referring to internal nodes by names which are often artificial and arbitrary (e.g. "cl0.mp2"). Likewise, simulation results are also displayed on the color screen. Edisim works at the logic level, and makes use of the switch-level simulator "isim" [Szym81]. Edicap works at the analogue voltage level, and is based on the timing simulator "emu" [Ackl81]. In edisim results are displayed by modulating the layout according to logic state: logic one is displayed in bright colors, logic zero as dark rectangles, and the X state as a rectangle with an "x" through it. Edicap can display results in a similar way, except that the X state corresponds to a voltage somewhere between the logic 0 and logic one threshold, rather than an unknown quantity. Edicap can also produce waveform plots of selected nodes merely by pointing to them on the color screen. Compared with the textual interface provided by most simulators, the graphic interface of edisim and edicap is simpler to learn and faster to use for both the novice and the experienced designer.