Deals with analytical testing of circuits, i.e. testing depending on the physical (and not logical) structure of circuits. Fault hypotheses concerning contacts, metallizations, etc... are made. Successively, a stage of an elementary adder, an elementary adder, a stage of the M6800 ALU and the M6800 ALU are addressed. Other typical circuits of data processing sections of CPUs are evoked. Finally the implementation of algorithms for the entire data processing section of the M6800 is evoked, together with further development