One of the major developments in electronics recently has been the explosion in the popularity of microcontrollers, in particular the PIC series of processors. A microcontroller is effectively a simple computer on a single chip, complete with microprocessor, input/output ports, RAM and ROM to contain the program. A single 18 or 28 pin PIC processor can often replace a dozen or more conventional logic. Also, the versatility of a microprocessor based design means that it is often possible to incorporate useful extras in the design that would be difficult for impossible using conventional logic circuitry.