The MSP430 is typically used in applications such as metering, intelligent sensing, control systems and portable instrumentation. In some systems, the microcontroller may need to interface to an external device such as a DSP co-processor to handle digital signal processing-intensive calculations and operations. This application note describes and provides a complete hardware and software reference design which includes frameworks running on both the MSP430 and DSP, as well as incorporating Inter Processor Communication (IPC) drivers to implement a simple message-passing scheme between the two processors. A Digital Audio Player is shown as an example. Supplied with this application note are complete reference frameworks for the MSP430 and DSP which can both be run out of the box and then subsequently adapted for other real-world system designs. The complete projects and source code are provided as separate packages for both the MSP430 and TMS320 platforms.