1996 Research Summaries for the Ptolemy Project

Mixed-Signal Simulation in the Ptolemy Environment

Researcher:Joel R. King
Advisor:Edward A. Lee
Sponsors:ARPA Contract F33615-93-C-1317 and the Ptolemy Project
The simulation of systems and circuits that are composed dually of analog and digital sections has received significant attention from the CAD community in recent years. This is because the simulation of circuits like analog to digital converters with traditional electrical simulators such as Spice is not cost effective due to the high overhead of the numerical algorithms used by electrical simulators. This has driven the creation of a new set of CAD tools which can simulate the analog and digital portions of a circuit with separate simulators, each of which is optimized for a particular topology (e.g., switch level simulator, electrical simulator, etc.)

The heterogeneous nature of the Ptolemy environment makes it a natural platform on which to do mixed-signal simulation. This coupled with the fact that gate level and switch level simulators have already been added to the Ptolemy framework makes it possible to create a flexible and powerful mixed-signal simulation environment within Ptolemy through the addition of an electrical simulator.

This research seeks to address the issues of coupling an electrical simulator to the Ptolemy environment by using prior work in the area of event driven simulation as a model [1]. The critical issues will be handling differences between the representation of time in the electrical simulator and in the domain to which the electrical simulator is coupled, the conversion of outputs and inputs into forms acceptable by outside domains and the electrical simulator, and the effective modeling of loading presented by ensuing stages and domains.

  1. K. A. Sakallah and S. W. Director, "SAMSON2: An Event Driven VLSI Circuit Simulator," IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, vol. CAD-4, no. 4, pp. 668-684, October 1985.
Send comments to Joel King at jking@eecs.berkeley.edu.