Descrição VHDL e prototipação em FPGA do processador MOS 6502

Abstract

The project described by this assignment consisted in revisiting the 6502 microprocessor, an integrated circuit widely used in 1970s and 1980s. The first two Apple computers, consoles and computers from Atari and the first Nintendo console are some examples of famous applications of this microprocessor. The project started with a study of the existing documentation about the processor in order to understand its original architecture and organization. The following stage consisted in defining the structure of the data path and control path, which were used as basis for the implementation. Posteriorly, we started the implementation in VHDL language following the diagrams built on the previous stage, whereas we seek to obtain a completely synthesizable circuit for both ASIC and FPGA design flows. In order to verify the implementation developed, we used the Spartan 6 FPGA as target hardware, which is available in Nexys 3 development kit. As validation in a real application, we used a HDL description of the Nintendo Entertainment System (NES). Thus, we could evaluate the behavior of the developed processor in a complex system, in which the computational load is high and there is interaction with other circuits. At the end of the project, we obtained a functional processor with support to the original instruction set.