A method for generating FPGA-based prototype systems capable of implementing UFS HS-G4 communication protocols using inexpensive/slow FPGAs. ASIC/SoC-targeted circuit designs are modified to include a speed converter that causes a UFS controller to generate transmitted data streams at one-half operating speed (e.g., 146 MHz) during HS-G4 operations, modifies the transmitted data streams to intersperse filler data values between transmitted data values, and transmits the modified data streams to M-PHY physical interconnect devices (PIDs) at full speed (e.g., 292 MHz). The speed converter also receives full-speed HS-G4 data streams that include both data and filler values and causes the UFS controller to operate at one-half operating speed (e.g., 146 MHz) such that only data values are read. PLD-based prototype systems that include separate M-PHY PIDs mounted on PCBs are efficiently configured to implement the modified circuit design. A prototyping tool automatically incorporates the speed converters into submitted ASIC/SoC-targeted circuit designs.