Design of bidirectional coherent counters

The general design theory of coherent parallel counters is described and illustrated by the design of a 5421 BCD counter. The method shows how the counter can be steered to operate bidirectionally. Details of design data for a number of differently coded bidirectional decade counters are also given. The circuits described use JK flip flops and have been fabricated using silicon integrated circuits in order to prove the theory. (In this paper, as in current usage, flip flops are bistable elements.)