Communications system for implementation of synchronous, multichannel, galvanically isolated instrumentation devices

An apparatus and method for synchronous communications using a serial data stream employs a housing with a controller and a back plane. The housing accepts one or more modules for interconnection with the back plane. The back plane distributes power to the modules and provides a communication link from the controller to each module. Each communication link includes a data out line, a data in line and a clock line, where each clock line is derived from one clock source.