The Pearl Language In Real-time Systems

For the time being, developing a real time control system becomes a hot pot. Theories and technologies are expected to be realistically applicable to the contiguous phases of the software development, for instance, in the process of from requirement engineering, system design to encoding path.In the article, author describes the basic categories of real time system, introduce some analyses and design methods of real time system in common use such as language description and mathematic analyses; flow chart; pseudo code and program design language (PDL); finite conformation machine and Petri net; analyze and compare the merit and demerit of those methods in summary; discuss the most complex and kernel crux of real time system, i.e., task assignment and scheduler algorithm. Emphasize on the scheduler algorithm to the single microprocessor, multi-task microprocessor and distributing system.Owing to the low efficiency, high expense and less code norm in developing the real time control program in China, which lead the maintenance nearly unavailable and waste to both man power and recourse, after researching a real time control language-PEARL which is widely spread in Europe, author concludes the basic characters of PEARL.Hi-PEARL, which assimilates the basic criteria of famous real time control program-EUCLID, is a highly integrated version of PEARL. This article emphasizes on the supporting mechanism of Hi-PEARL value added characters to encoding a real time control system. Such as how to utilize SHARED-VARIABLE properties and a limit time LOCK sentence to perform a better parallel processing control; in the time operation chart, use SEIZE, FREE, FREE-AFTER, NEXI-SOLT-AVAILABLE functions to identify tasks and synchronize resources; how to adopt the REPEAT function with MAXLOOP property to terminate the endless loop implement; use the configuration of PARELL and ACTIVITY to support other parallel mechanism than tasks.Researching and summarizing those characters of PEARL in detail,author encodes a PEARL program applied to pressure-measurement control system. It shows the strongest function of PEARL in the real time control.