An Action System Speci cation of the CaltechAsynchronous

The action system framework for modelling parallel programs is used to formally specify a microprocessor. First the microprocessor is speciied as a sequential program. The sequential specii-cation is then decomposed and reened into a concurrent program using correctness-preserving program transformations. Previously this microprocessor has been speciied in a semi-formal manner at Caltech, where an asynchronous circuit for the microprocessor was derived from the speciication. We propose a speciication strategy that is based on the idea of spatial decomposition of the program variable space. Applying this strategy we give a completely formal derivation of a high level speciica-tion for the Caltech microprocessor. We also demonstrate the suitability of action systems and the stepwise reenement paradigm for formal VLSI circuit design.