Getting to a test standard for mixed-signal boards

Testing mixed-signal boards is a crucial issue for the next decade since boards are not only digital, for which the test problem is already solved by the IEEE1149.1 test bus, but mixed analog-digital. A standard is under preparation and is called IEEE P1149.4 "Mixed-Signal Test Bus Standard". Several international companies and R&D institutions are organized in a Working Group. This WG defines the future standard and discusses the problems of analog test as well as the compatibility with the IEEE1149.1 and other standards. Recently a test chip has been fabricated. Its measurement should allow the IEEE1149.4 committee to evaluate the various testability structures. The present situation of the standard consists in adding two analog busses to the 5 pins of the IEEE1149.1 digital test bus. Several other functionalities are under development.