a serial stream interface for combining a master serial data stream comprising a sequence of n - bit master data packets and a slave serial data stream comprising a sequence of n - bit slave data packets . the serial stream interface comprises : 1 ) a slave input interface comprising a slave buffer having a serial input for receiving the slave serial data stream and an n - bit slave parallel output for outputting each of the n - bit slave data packets wherein the slave buffer stores each n - bit slave data packet using at least one slave timing signal associated with the slave serial data stream ; 2 ) a source selection circuit having a first input channel for receiving an n - bit master parallel output from a first master data source and a second input channel coupled to the n - bit slave parallel output ; and 3 ) a serialization circuit having an input coupled to an output of the source selection circuit for receiving a selected one of the n - bit master parallel output and the n - bit slave parallel output and a serial output , wherein the serialization circuit sequentially shifts out each bit of the selected one of the n - bit master parallel output and the n - bit slave parallel output .