US Patent 7482834 Programmable multiplexer

An implementation of multiplexer functionality using a multiplexer having half the number of input ports as it has possible output values is provided. A multiplexer having two data input ports performs the function of a multiplexer having four predetermined data input signals (A1, A2, A3, A4). In general, a multiplexer having only m data input ports performs the function of a multiplexer having twice as many predetermined data input signals A1, A2, . . . , Aj, where j=m*2. The multiplexer functionality may be implemented using a programmable device having one or more macrocells, an inverter and switches such as antifuses.