Interconnection and Noise Immunity of Circuitry in Digital Computers

This paper describes the mutual dependence of interconnection and noise immunity in digital circuitry. Utilizing the charge control concept, the static thresholds of a transistor are defined in terms of the saturation charge and the depletion layer charge. These are subsequently translated into dynamic thresholds of circuitry by means of the network theory. The various noises encountered in digital computers are outlined. The noise due to interconnections is discussed in detail, and remedies are suggested. Design criteria for interconnections are then formulated by selecting the impedance and the routing of the wiring according to the noise margins of the circuits. Engineers are encouraged to view the system as a whole and to treat interconnections as an integral part of circuit design. A numerical example serves to illustrate the important points.