Designing a Custom CPU Architecture Based on Hardware RTOS and Dynamic Preemptive Scheduler

Abstract

The current trend in real-time operating systems involves executing many tasks using a limited hardware platform. Thus, a single processor system has to execute multiple tasks with different priorities in different real-time system (RTS) work modes. Hardware schedulers can greatly reduce event trigger latency and successfully remove most of the scheduling overhead, providing more computing cycles for applications. In this paper, we present a hardware-accelerated RTOS based on the replication of resources such as program counters, general purpose registers (GPRs) and pipeline registers. The implementation of this new concept, based on real-time event handling implemented in hardware, is intended to meet the current rigorous requirements imposed by critical real-time systems. The most important attribute of this FPGA implementation is the time required for task context switching, which is only one clock cycle or three clock cycles when working with the atomic instructions used in the case of inter-task synchronization and communication mechanisms. The main contribution of this article is its focus on mutexes and the speed of response associated with related events. Thus, fast switching between threads is also validated, considering the handling of events in the hardware using HW_nMPRA_RTOS (HW-RTOS). The proposed architecture implements inter-task synchronization and communication mechanisms with high performance, improving the overall response time when the mutex or message is expected to relate to a higher-priority task.

Keywords

• embedded systems
• field-programmable gate arrays (FPGAs)
• real-time mutex event handling
• task scheduling