Approximating linear time with finite count clocks

Resumo

In computer systems, actions are trigered, not only by external events, but also by passing of time. In the case of real-time systems, these actions must be executed under strict time constraints. Deciding on what actions to take depends on the correct result of operations like comparing time instants. These are complicated by the fact that clock counters have a limited life span. If care is not taken, their wrap-around may present problems and limit the operating life of a system. We present a simple method to circumvent this problem, based on a counter that has a life span of twice the larger interval of interest. This method is easily and efficiently implemented by using the type cast facilities of language such as C.