Implementing the Bus Protocol of a Microprocessor in a Software-Defined Computer

Julia Kosowska , Grzegorz Mazur

Abstract

The paper describes a concept of a software-defined computer imple-mented using a classic 8-bit microprocessor and a modern microcontroller with ARM Cortex-M core for didactic and experimental purposes. Crucial to this de-sign is the timing analysis and implementation of microprocessor’s bus protocol using hardware and software resources of the microcontroller. The device de-scribed in the paper, SDC_One, is a proof-of-concept design, successfully demonstrating the software-defined computer idea and showing the possibility of implementing time-critical logic functions using a microcontroller. The project is also a complex exercise in real-time embedded system design, pushing the mi-crocontroller to its operational limits by exploiting advanced capabilities of se-lected hardware peripherals and carefully crafted firmware. To achieve the re-quired response times, the project uses advanced capabilities of microcontroller peripherals – timers and DMA controller. Event response times achieved with the microcontroller operating at 80 MHz clock frequency are below 200 ns and the interrupt frequency during the computer’s operation exceeds 500 kHz.