TROUBLE DIAGNOSTIC SYSTEM OF CIRCUIT ELEMENT, DIAGNOSTIC METHOD AND DIGITAL PROCESSOR SYSTEM

摘要

PURPOSE: To provide a diagnostic system for diagnosing the state of a circuit element capable of scanning a scannable circuit without obstructing the state of an unscannable circuit for violating the protocol of a bus to which an unscannable device is attached. CONSTITUTION: A processor interface circuit is connected through a processor bus between a microprocessor and a scannable processor circuit 24 and the scannable processor is insulated from the unscannable microprocessor 22. The processor interface circuit is also scannable and a memory element for affecting the bus by preventing scanning during the use of the bus is provided. Scanning is prevented by maintenance request signals sent from a scanning controller to the processor interface circuit and maintenance approval signals sent from the processor interface circuit to the scanning controller.