Physical signals, events and digital streams

A revision of IEEE Std 1641 is coming to an end and is undergoing its approval cycle. This standard, which provides a method of accurately defining signals and tests, has been further developed with many improvements. The use of signals and events has now been extended to include digital signals. These three elements, physical signal streams, event streams and digital streams, provide the vital backbone to the description of all signals, simple or complex. They define when a signal may exist and when it may not, when a signal has a value and when it has not, when it starts and when it stops. Understanding the operation of SignalFunctions of different types and the operation of the signal, event and digital streams is essential to the building of Test Signal Framework (TSF) models, especially those which include complex timing relationships. This paper explains each of these streams and how they interact one with another.