With the rapid development in digitalization technology, the digital electronic product has become an indispensable appliance in the daily life of modern people. The technology of allowing two or more electronic products to share and distribute data with each other is increasingly gaining great significance. Universal serial bus (USB) is by far the most popular data communication interface because of its high data transmission rate, hot-swappable functionality and plug-and-play (PnP) capability. The advantages of the USB data communication interface have provided adequate flexibility for the development and research in the application of electronic product. The leading companies in the field of computer product manufacturing have been striving for the presentation of electronic products with a USB interface. However, the conventional electronic device with a USB interface is generally designed as a USB device, which indicates the electronic device can conduct data communication with other USB devices only when it is connected to an information-processing product provided with a USB host controller (e.g. a host computer). Without the aid of a host computer, two or more USB devices can not conduct mutual data communication with each other. This would limit the utility of a USB device when it is desired to perform data communication with other devices. Hence, the technology that provides a USB controller to allow two or more USB devices to conduct peer-to-peer data communication without the need of a host computer has become a prospect that most of the computer manufacturer are striving for.
Certain of the computer manufacturers dedicated their efforts to promote an extended version of the USB data communication interface standard, namely USB On-The-Go (USBOTG), which attempts to enable all the electronic products complying with USB OTG standard to conduct data communication without the intervention of a host computer. A conventional USB OTG controller is illustrated in FIG. 1. The USBOTG controller 10 shown in FIG. 1 is founded based on an extension of USB 2.0 standard, and comprising a host controller 11, a device controller 13, and an OTG controller 19, wherein the host controller 11 is used for carrying out the host mode operation, and the device controller 13 is used for carrying out the device mode operation. Both of the host controller 11 and the device controller 13 are connected to the OTG controller 19, and the OTG controller 19 is capable of detecting whether the device connected to a USB connection port is a USB device or a USB OTG device via the ID signal line 191. If the device connected to the USB connection port is a USB device, the OTG controller 19 manipulates the USB transceiver 171 to be connected to the D+ signal line 151 or D− signal line 152 in order to conduct data communication with the USB device. If the device connected to the USB connection port is a USB OTG device, the OTG controller 19 manipulates the OTG transceiver 173 to be connected to the D+ signal line 151 or D− signal line 152 in order to conduct data communication with the USB OTG device. In addition, the OTG controller 19 is further capable of detecting the potential on the ID signal line 191 to determine whether the USB OTG controller is to conduct data communication with the connected device under the host mode or under the device mode.
The aforementioned USBOTG controller is capable of conducting peer-to-peer bi-directional data communication with an electronic device having a USB interface or a USB OTG interface without the need of a host computer. However, the circuit architecture of a USB OTG controller is more complicated than that of a USB controller, in which an OTG controller is required and an OTG transceiver is essential because the potential required in the data communication in a USB OTG controller is different with that in a USB controller. Consequently, the manufacturing cost of a USB OTG controller is significantly boosted due to the magnificent alteration in the circuit architecture. More disadvantageously, the USB communication protocol is necessary to be modified in response to the adaptation of the USB OTG controller, which will burden the product development of a USB device manufacturer and designer.