Test signal generator on substrate to test

摘要

A test system is added to a substrate and a test mode of operation is added to the timing and control functions of a system on the substrate. When a multifunctional system on the substrate is tested, a first functional subsystem is connected to an external tester. The tester causes the timing and control system to enter the test mode of operation. When in the test mode of operation, the test system provides a signal derived from a signal generator on the substrate. The generated signal is coupled to a second functional subsystem so that functional independence of the first and second subsystems can be verified.