A relationship between a maximum bit rate and circuit parameters of FSK-based simultaneous wireless power and data transfer system with a magnetic resonance wireless power transfer (MR-WPT) circuit is considered. The time required for switching between the two FSK carrier frequencies is formulated as a function of the circuit parameters. A design procedure for circuit parameters to achieve the desired bitrate is proposed. The validity of the example parameters determined by the proposed design procedure is confirmed by the transient simulation.