A new testing philosophy-differential test

A new testing philosophy is proposed which takes advantages of both off-line and on-line testing strategies. A differential testing scheme (DT) is developed based on the new testing philosophy. The DT is capable of testing digital systems on-line without any error detection code but with an initialization at the very beginning. In the forced initialization, at least one-hour random test pattern generation is required if a CPU runs at 20 MHz. Using the natural initialization, the DT will not be effective until the system has run several days or weeks. This means that, once the DT is started by the initialization, it starts without end until power is turned off