Patent ID: 7707336

Claim:
A USB system with single port connecting to an external circuitry, comprising: a USB port for connecting to the external circuitry; a speed detection circuitry electrically coupled to the USB port for detecting a transmission speed between the USB system and the external circuitry via the USB port, and outputting a first detecting result and a second detecting result; a start of frame (SOF) generator electrically coupled to the speed detection circuitry for receiving the second detecting result directly from the speed detection circuitry and outputting a SOF signal, and determining a cycle of the SOF signal based on the second detecting result; and a host controller electrically coupled to the SOF generator and the speed detection circuitry for receiving the SOF signal directly from the SOF generator and the first detecting result from the speed detection circuitry, wherein the host controller has a state machine, wherein the host controller masks a part of functions in a queue head and an isochronous transaction descriptor and adjusts the state machine based on the first detecting result, and the host controller is adjusted based on the cycle of the SOF signal received from the SOF generator to make the USB system comply with the standards of USB 2.0, USB 1.1 and USB 1.0, wherein the speed detection circuitry detects whether the transmission speed of the USB port is high speed (HS), full speed (FS), or low speed (LS), wherein when the host controller determines that the first detecting result is the full speed or the low speed, a high bandwidth pipelined multiplier and a counting of the reloaded negative response character among the functions in the queue head are both masked, and an end point speed function among the functions in the queue head is set to a reserved state.