Structured Microcontroller Design Using PLA Firmware

摘要

The objective of this research is to contribute a design methodology for microprogramming architectures with supporting firmware and development tools. Two PLA-based microcontrol architectures have been proposed that are suitable for modular microprogramming. The first scheme consists of a PLA sequence store, a microcode ROM and an address processor. This structure has the capability of complex microsequencing such as multiway branching, microsubroutines, nested microlooping and the like. To alleviate the pin-limitation problem, a bit-slice approach is taken in the second scheme which allows for easy microcontrol expandability and compaction of the sequence store. Firmware support for the microcontrollers is provided by such control constructs as if-then-else, while-do and the like, which are available at the microlevel. Several firmware design tools have been developed and incorporated into a software package, MMDS, a Modular Microprogram Development System. MMDS includes the following tools: a microcode assembler, a microsequencer assembler, a PLA code formatter and a functional-level simulator of modular microarchitectures. Keywords: VLSI microcode; programming languages.