1. A data processing device, comprising: a central processing unit (CPU) for executing instructions; a memory circuit connected to the CPU for storing a plurality of instructions which are executed by the CPU; serial port interface circuitry connected to the CPU, operable to transmit and receive data with dual phase frames; and wherein the serial port interface circuitry comprises at least a first control register operable to be loaded by an instruction executed by the CPU, wherein the first control register is operable to select a first set of parameters for a first phase of the dual phase frame and further operable to select a second set of parameters for a second phase of the frame, such that the first set of parameters comprise a first phase number of words per frame and the second set of parameters comprise a second phase number of words per frame.