Digital realization of analogue computing elements using bit streams

Real-time execution of an algorithm can be achieved with a fast serial processor or with a parallel machine. Usually both of these methods use multi-bit binary words which are processed by an arithmetic unit. This paper demonstrates an alternative approach to the parallel solution. Here, instead of a multi-bit word, a single bit-stream is processed by digital logic to satisfy the required algorithm. Using elementary digital gates, classical elements like integrators and differentiators can be constructed. These elements operate on bit-streams and also produce bit-streams and by interconnecting them, complex systems can be built. The inherently parallel nature of this technique makes it possible to implement complex algorithms in real time. This technique has been successfully applied to implement a PID controller on an FPGA for an experimental thermal plant.