Abstract: Apparatus and a method for testing tiered digital multiplexing apparatus. To test a primary train of tiered demultiplexers, a data path assurance train of demultiplexers and a selector is used to generate a demultiplexed signal for comparison with a primary demultiplexed signal. To test a primary train of tiered multiplexers, the output of the final multiplexing stage is connected to the input of the data path assurance train of demultiplexers to generate a demultiplexed signal for comparison with a primary input signal to the primary multiplexer train. Advantageously, a simpler, more reliable, and less expensive data path assurance circuit using the same types of components as the primary multiplexers and demultiplexers can be used to detect failures in these primary units as well as the data path assurance circuit.

Abstract: The disclosure relates to methods of forming Insulated Gate Field Effect transistors and the product suitable for integrated circuits with channel lengths of 1 micron or less, the transistors being isolated from other transistors or other components in the circuit without the requirements of extra isolation steps. This is provided by means of a double diffusion which isolates the channel of the transistor from other elements in the circuit. Channel length is solely a function of the diffusion schedule through openings in the oxide through which the double diffusion takes place.