Controlling circuit

A controlling circuit, applicable to bridge a universal serial bus (USB) host device and at least one storage device, the controlling circuit comprising:

• a routing circuit, comprising an adapter circuit and an enhanced superspeed function circuit;
• an upstream facing port interface circuit, coupled to the USB host device, the adapter circuit, and the enhanced superspeed function circuit based on a first transmission specification;
• and
• a downstream facing port interface circuit, coupled to the adapter circuit, the enhanced superspeed function circuit, and the at least one storage device based on a second transmission specification,
• wherein the adapter circuit is coupled to the downstream facing port interface circuit through the enhanced superspeed function circuit based on a first tunneling protocol to form a first transmission path, and coupled to the downstream facing port interface circuit through the upstream facing port interface circuit and the enhanced superspeed function circuit based on a second tunneling protocol to form a second transmission path.