A CMOS Integrated Circuit is a device that performs quadrature decoding, counter, and bus interface functions. Decoder Integrated Circuits are designed to improve system performance in both digital closed loop motion control and digital data input systems. The device manages this task by shifting time intensive quadrature decoder functions to cost effective hardware. The decoder IC itself consists of quadrature decoder logic, binary up/down state counter, and an 8-bit bus interface. The use of Schmitt-triggered CMOS inputs and input noise filters allow reliable decoder IC operation in noisy environments. This decoder IC contains a 12-bit counter and provides TLL/CMOS compatible tri-state output buffers.