ISSN 1000-1239 CN 11-1777/TP

计算机研究与发展 ›› 2021, Vol. 58 ›› Issue (6): 1176-1191.doi: 10.7544/issn1000-1239.2021.20210157

所属专题: 2021计算机芯片关键技术前沿与进展专题

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  1. (中国科学技术大学计算机科学与技术学院 合肥 230027) (
  • 出版日期: 2021-06-01
  • 基金资助: 

A Real-Time Processor Model with Timing Semantics

Wang Chao, Chen Xianglan, Zhang Bo, Li Xi, Wang Chao, Zhou Xuehai   

  1. (School of Computer Science and Technology, University of Science and Technology of China, Hefei 230027)
  • Online: 2021-06-01
  • Supported by: 
    This work was supported by the National Natural Science Foundation of China (61772482).

摘要: 实时嵌入式系统是安全关键设备的计算与控制核心.为了保证系统的时间行为正确,要求其软硬件具有时序确定性和可预测性.而现代计算机系统的各个抽象层次均缺乏时间语义,无法满足硬实时安全性设计要求.针对指令集体系结构层次的基础设施缺乏时间语义的问题,尝试重新定义实时嵌入式系统的指令集和微体系结构.首先,提出一种具有时间语义的实时计算机体系结构模型——实时机(real-time machine, RTM).接着,参考时间触发自动机理论,构建具有时间语义的指令集——TTI(time-triggered instruction set)作为RTM的软硬件接口,并讨论TTI的时间语义完备性问题.最后,设计并实现了实时处理单元(real-time processing unit, RPU),通过理论分析与实验结果的对照得出RPU的时序确定性.逻辑执行时间(logical execution time, LET)编程模型是学术界广泛认可的实时编程范式,通过给出在RPU上运行LET任务集的示例,说明RTM和TTI的有效性.

关键词: 实时嵌入式系统, 时间可预测性, 实时机模型, 时间语义指令集, 实时处理器

Abstract: Real-time embedded system (RTES) is the core of calculation and control of safety-critical equipment. The software and hardware of RTES are required to have timing determinism and timing predictability to ensure the correctness of its time behavior. However, nearly every abstraction of modern computer systems has failed to provide timing semantics, which means it cannot meet the security design requirements of hard real-time systems. In this paper, we focus on the lack of timing semantics in the infrastructure of the instruction set architecture and try to redefine the instruction set and microarchitecture of RTES. First, we propose real-time machine (RTM), a real-time computer architecture model with timing semantics. Then, referring to the theory of time-triggered automata, we construct TTI, which is a timed instruction set, as the software/hardware interface of RTM. We also discuss the completeness of the timing semantics of TTI. Finally, we design and implement the real-time processing unit (RPU) and the timing determinism of RPU is obtained by comparing theoretical analysis with experimental results. The LET programming model is a real-time programming paradigm widely recognized by academia. In this article, we illustrate the effectiveness of RTM and TTI by giving an example of running LET tasks on RPU.

Key words: real-time embedded system (RTES), timing predictability, real-time machine (RTM), timed instruction set, real-time processor