A computer aided design automation system for developing microprogrammed processors: a design approach through HDLs

Abstract

This paper presents an approach that provides a total computer aided design environment for developing microprogrammed processors using hardware description languages. This includes the behavioral description, micro-coding, and testing of the integrated microprogrammed processors. To illustrate the design procedure a functionally equivalent micro-coded version of the Motorola's MC6809 processor was modeled, and tested. The results indicate that it is a valid design approach. The micro control unit described through the hardware description language AHPL not only replaces the required microprogram simulator but also emulates its exact hardware. Here the micro control unit and the microcode are emulated and tested as a unit: in such the same way a real processor's micro control unit functions with its stored microcode. The emulated micro-simulator here is used for verifying the MC6809 microcode. It can, however, be used as a general purpose testbed for testing any microcode. The design procedure presented here is for the MC6809 microprogrammed processor, however, the procedure can be used to design any processor with user defined instruction set.