Design methodology and microdiagnostics development for a self-checking microprocessor

The conventional design of electronic circuits is intolerant to operational faults. Self-checking logic is aimed at online fault detection and can hence be incorporated to achieve reliable operation. In this paper, the design of a self-checking microprocessor is discussed. Self-checking strategies for different functional units are selectively and judiciously applied, and also modified wherever necessary, for the design of the register section, the arithmetic & logic unit and the control unit. A self-checking microprogrammed control unit, capable of supporting normal instruction execution concurrently with diagnostics, is developed. The design methodology has been applied to Intel's 8085A microprocessor as a case study to make it self-testing. Overheads involved have also been estimated.