In many aspects of microprocessor systems design and diagnosis, temporal reasoning of a sequence of event changes occurring at imprecisely known time instants is often required. By combining the change-based and time-based approaches of temporal logics, the concept of time range is proposed as a key component of an enhanced time structure which captures the notion of time impreciseness in event occurrence. A practical MC68000 CPU-memory interface design problem is used as an extensive example to illustrate the various temporal reasoning techniques derived from this new time structure. Efficient methods for time referencing, constraint satisfaction and propagation of time ranges have been developed for embedding domain knowledge in a deep-level constraint model. It is also shown how different shallow rules (regarded as expert's rule of thumb) for system diagnosis can be generated and explained through an inference process of the constraint model.