Error secure/propagating concept and its application to the design of strongly fault-secure processors

A concept of the error-secure and the error-propagating interfaces of the subsystems in a digital system is introduced, and shown to be useful for practical design and verification for a strongly fault-secure system which is known to achieve the totally self-checking (TSC) goal. A sufficient condition is shown for subsystem interfaces to meet for it to be possible to construct a strongly fault-secure system with no checkers used to monitor the embedded interfaces. On the basis of the error-secure/propagating concept, a design is presented for a strongly fault-secure microprocessor which implements the instruction set of Intel´s i8080 8-b microprocessor. In the design, a complete set of building blocks is defined and all the partial interfaces are verified for the error secure/propagating property. Only four checkers are used at the embedded interfaces in the resulting strongly fault-secure processor