MONITORS OF VARYING COMPLEXITY FOR CONCURRENTLY TESTING MICROPROGRAMMED CONTROL UNITS.

An outline is presented of methods for designing monitor circuits that can be used to test any general microprogrammed control unit (MCU) concurrently. The basic monitor, tailormade for a given MCU, uses a circuit that generates keys of check bits and compares them to those stored in each microinstruction (state). The keys are defined over states within the MCU, described as a sequential machine by a flow table. A spectrum of monitors can be designed with different complexities determined by the method of generating the keys. The most complex design uses a mapping function feedback shift-register for key generation. An intermediate design combines both approaches to predict keys. The general monitor can be designed to detect any fault in a specified fault set.