Design And Implementation Of PSEFM-Cassandra For Supporting Timing Semantics

Safety-critical systems is a system whose failure may result in disastrous con-sequences.Safety-critical systems,whose main characteristic is the demand for pre-dictable timing behaviors,have suffered a complexity growth as the number of services continuously increases in these systems.Experience has shown that this issue cannot be solved by software alone but rather requires support from the processor.A lot of model is applied to tackle this issue.However,without domain-specific hardware sup-ports,timing expressing usually rely on periodic timer interrupts of operating systems,yielding limited timing precision for the significant kernel delay and enormous jitter of tasks executions.This thesis starts with the definition of the predictability of the safety-critical system.Then we analyze the timing constraints for the systems' behav-ior.By designing an extended time trigger instruction set,we design an architecture and programming framework that supports time semantics,so that the input/output and task computing behaviors with time constraints can reach the processor cycle accurate granularity.The main work of this article includes:1.This thesis defines the predictability for safety-critical systems which under com-plex environment interactions.Then,we analyze the requirements of the temporal semantic with added time semantics of the systems.2.Aiming at the current situation that the traditional architecture lacks timing at-tributes,we propose a Time-Triggered Instruction set,named TTI,to tackle this issue by augmenting the ISA with timing properties to support predictable se-mantics in programming level.The instruction set consists of three types of in-structions:timing information instructions,time triggered event instructions,and time triggered I/O instructions.We believe that the instruction set can describe the timing behavior explicitly.3.Based on the Nios II soft core,we implemented a coprocessor to support the TTI,named Cassandra.This coprocessor consists of a control unit,a time management module,an event management module,and an I/O management module.4.To enable programmers to use TTI and Cassandra coprocessor more easily,we propose a programming framework named PSEFM-Cassandra.The program-ming framework uses the time-triggered mechanism in the coprocessor to imple-ment the input,computation,and output behavior of the task.During the runtime,the processor does not have to use the clock interrupt to measure time.Then,we introduces how the PSEFM-Cassandra constructs LET task.5.This thesis evaluates the performance of the implemented PSEFM-Cassandra pro-gramming framework,and concludes that the architecture of the instruction set makes it easier to obtain the Input-Determined program than the traditional archi-tecture.