Universal serial bus device initialized with a real descriptor stored in host and method for initializing the same

A universal serial bus (USB) device and an initializing method therefor. The USB device includes an interface, at least one signal line and a voltage regulator. The interface stores a basic descriptor. The interface primarily activates an initialization signal and transfers the basic descriptor to a host to perform a primary initialization. Further, the interface downloads a real descriptor stored in the host in response to a download command generated from the host, and secondarily activates the initialization signal and transfers the real descriptor to the host to perform a secondary initialization. The signal line guides the basic descriptor, the real descriptor and the download command. The voltage regulator pulls up the signal line while the initialization signal is activated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a universal serial bus (USB) device, and more particularly, to a USB device to be initialized with a real descriptor stored in a USB host, and a method for initializing the same.

2. Description of the Related Art

A USB device is an interfacing device for connecting peripheral equipments, such as a keyboard, a monitor, a mouse, a printer, a modem, a digital camera, etc., to a USB host. The USB device is initialized to allow the peripheral equipments to communicate with the USB host. Meanwhile, the USB host stores a real descriptor and a descriptor recognizing program to initialize the USB device.

FIG. 1is a block diagram of a conventional USB device. In the conventional USB device shown inFIG. 1, a descriptor read/write portion12of a USB interface10reads a descriptor REDES stored in an additional memory20and then, transfers the descriptor REDES to a register14. The transferred descriptor REDES is stored in the register14. The descriptor REDES includes the information of a real vendor I.D. and a real product I.D. for a USB host1.

An initialization signal generator18in the USB interface10activates an initialization signal XINT, and a voltage regulator30pulls up a signal line40, in response to the initialization signal XINT. That is, a transistor32in the voltage regulator30is turned on, and then a terminal voltage VDDis transferred to the signal line40through a resistor34.

The descriptor read/write portion12reads the descriptor REDES stored in the register14at need, and provides the descriptor REDES to the USB host1through a USB core16and the signal line40. When a descriptor recognizing program1aof the USB host1recognizes the descriptor REDES provided from the USB interface10, the initialization of the conventional USB device is completed.

Generally, the additional memory20is a ROM (Read Only Memory) positioned at an outside of the USB interface10, so that the descriptor REDES can be changed depending on the USB host1.

However, the conventional USB device has disadvantages in points of the chip size and the manufacturing cost due to the additional memory20positioned at the outside of the USB interface10.

SUMMARY OF THE INVENTION

In one aspect, there is provided a USB device to be initialized as a state enabling a communication with a host. The host stores a real descriptor and a descriptor recognizing program. The USB device includes an interface, at least one signal line and a voltage regulator. The interface stores a predetermined basic descriptor. The interface primarily activates an initialization signal and transfers the basic descriptor to the host in order to perform a primary initialization. Further, the interface downloads the real descriptor in response to a download command generated from the host, and then secondarily activates the initialization signal and transfers the real descriptor to the host in order to perform a secondary initialization. The signal line guides the basic descriptor, the real descriptor and the download command. The voltage regulator pulls up the signal line while the initialization signal is activated.

In another aspect, a USB device includes at least one signal line and an interface. The signal line is connected to a host. The signal line guides data and commands to the host. The interface stores a predetermined basic descriptor. The interface primarily activates an initialization signal and transfers the basic descriptor to the host in order to perform a primary initialization. Further, the interface downloads a real descriptor in response to a download command generated from the host, and then secondarily activates the initialization signal and transfers the real descriptor to the host in order to perform a secondary initialization. This interface includes a voltage regulator pulling up the signal line while the initialization signal is activated.

In still another aspect, there is provided a method for initializing a USB device connected to a host, which stores a real descriptor and a descriptor recognizing program. The initializing method comprises the steps of (a) performing a primary initialization with a basic descriptor stored in a ROM type memory; (b) receiving the real descriptor and a download command generated from the host; and (c) performing a secondary initialization with the real descriptor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2is a block diagram of a USB device according to one exemplary embodiment of the invention. Referring toFIG. 2, the USB device includes a USB interface100, a voltage regulator200and at least one signal (D+or D−) line250.

The USB interface100has a basic memory110, a descriptor read/write portion120, a register130, a command analyzing portion140, a timer150, an initialization signal generator160and a USB core170. The USB interface100manages communication on the basis of a USB protocol.

The basic memory110stores a basic descriptor BADES. When a ROM (Read Only Memory) is used as the basic memory110, even if an external power supplied to the USB interface100is cut off, the basic memory110stores the basic descriptor BADES. The basic descriptor BADES includes a common vendor I.D. and a common product I.D., and can be inputted to the basic memory110when the USB device is manufactured. Therefore, the information in the basic descriptor BADES can be different from real information for a USB host1connected to the USB device.

The descriptor read/write portion120reads the basic descriptor BADES stored in the basic memory110, when the external power is supplied to the USB interface100. The descriptor read/write portion120transfers the basic descriptor BADES to the USB host1, when the signal line250is primarily pulled up, through the USB core170and the signal line250. In this case, when a descriptor recognizing program1aof the USB host1recognizes the basic descriptor BADES transferred from the USB device, a primary initialization of the USB device is completed. Then, the USB host1provides a real descriptor REDES and a download command to the USB core170, through the signal line250. The real descriptor REDES includes a real vendor I.D. and a real product I.D. for the USB host1.

The descriptor read/write portion120downloads the real descriptor REDES in response to a download start signal XDST, which instructs a download of the real descriptor REDES, and transfers the real descriptor REDES to the register130. The descriptor read/write portion120activates a download completion signal XDEND, when the download operation is completed. With a predetermined period, the signal line250is secondarily pulled up. Then the descriptor read/write portion120reads the real descriptor REDES stored in the register130and transfers the real descriptor REDES to the USB host1, through the USB core170and the signal line250.

The register130stores the real descriptor REDES transferred from the descriptor read/write portion120.

The command analyzing portion140receives the real descriptor REDES and the download command provided from the USB host1, and activates the download start signal XDST. Then, the command analyzing portion140provides the download start signal XDST and the real descriptor REDES to the descriptor read/write portion120.

The timer150primarily activates a control signal XCON in the form of pulse, in response to the download completion signal XDEND. The timer150secondarily activates the control signal XCON with a predetermined period. The control signal XCON controls the initialization signal generator160. The secondary activation of the control signal XCON is generated before the descriptor read/write portion120transfers the real descriptor REDES to the USB host1.

An initialization signal XINT is primarily activated when the external power voltage is supplied to the USB device. The initialization signal XINT controls the voltage regulator200. The primary activation of the initialization signal XINT is terminated in response to the primary activation of the control signal XCON, and the initialization signal XINT is secondarily activated in response to the secondary activation of the control signal XCON.

The USB core170is connected to the USB host1via the signal line250. The USB core170receives the download command and the real descriptor REDES from the USB host1, and transfers them to the command analyzing portion140. The USB core170receives the basic descriptor BADES and the real descriptor REDES from the descriptor read/write portion120, and transfers them to the USB host1through the signal line250.

The voltage regulator200has a transistor210connected to a terminal voltage VDDand a resistor220. The resistor220is positioned between the transistor210and the signal line250. The transistor210is turned on while the initialization signal XINT is in the state of the primary or the secondary activation. Then, the voltage regulator200supplies the terminal voltage VDDto the signal line250, and the signal line250is pulled up. In this case, the USB device can transfer/receive data, such as the real descriptor REDES, the basic descriptor BADES etc., and the download command to/from the USB host1through the signal line250.

Meanwhile, the voltage regulator200is turned off when the initialization signal XINT is terminated. In this case, the signal line250is pulled down and the communication between the USB device and the USB host1is terminated.

FIG. 3is a flowchart for explaining a method of initializing the USB device illustrated in FIG.2. Referring toFIG. 3, in the method for initializing the USB device, an external power is supplied to the USB device, at step S305. Then, the initialization signal generator160primarily activates the initialization signal XINT, at step S310. In this case, the transistor210of the voltage regulator200is turned on and the terminal voltage VDDis transferred to the signal line250, at step S315. That is, the signal line250is pulled up.

Simultaneously, the descriptor read/write portion120reads the basic descriptor BADES stored in the basic memory110and transfers the basic descriptor BADES to the USB host1through the USB core170and the signal line250, thus the primary initialization is performed, at step S320. When the descriptor recognizing program1aof the USB host1recognizes the basic descriptor BADES, the primary initialization of the USB device is completed. In this state, the USB host1provides the real descriptor REDES and the download command to the USB interface100through the signal line250.

In this case, the command analyzing portion140receives the real descriptor REDES and the download command through the USB core170, at step S325. The command analyzing portion140generates the download start signal XDST and provides the real descriptor REDES to the descriptor read/write portion120. Then, the descriptor read/write portion120downloads the real descriptor REDES from the command analyzing portion140in response to the download start signal XDST, at step S330, and transfers the real descriptor REDES to the register130, at step S335. Thereafter, the descriptor read/write portion120activates the download completion signal XDEND.

In this case, the timer150primarily activates the control signal XCON in response to the download completion signal XDEND. Then, the initialization signal generator160terminates the primary activation of the initialization signal XINT in response to the primary activation of the control signal XCON, at step S340. The transistor210of the voltage regulator is turned off, and the transferring of the terminal voltage VDDto the signal line250is cut off, at step S345. Therefore, the communication between the USB host1and the USB device is terminated. The USB host1ignores the basic descriptor, which is recognized by the descriptor recognizing program1aduring the primary initialization of the initialization signal XINT.

With enough time such that the USB host1can completely ignore the basic descriptor, the timer150secondarily activates the control signal XCON. Then, the initialization signal generator160secondarily activates the initialization signal XINT in response to the secondary activation of the control signal XCON, at step S350. Therefore, the transistor210of the voltage regulator200is turned on again, and the terminal voltage VDDis transferred to the signal line250again, at step S355. That is, the signal line250is pulled up again.

Simultaneously, the descriptor read/write portion120reads the real descriptor REDES stored in the register130and transfers the real descriptor REDES to the USB host1, thus a secondary initialization of the USB device is performed, at step S360. Then, when the descriptor recognizing program1aof the USB host1recognizes the real descriptor REDES transferred from the descriptor read/write portion120, the secondary initialization of the USB device is completed. That is, the USB device of the invention is able to communicate with the USB host1. In this case, by the secondary initialization, the initialization of the USB device is completed.

As described above, since the USB device is initialized with the real descriptor REDES provided from the USB host1, the USB device does not require an additional memory positioned at outside of the USB interface100. Therefore, the size and the manufacturing cost of the USB device according to the invention can be reduced.

In the above embodiment, the voltage regulator200is separated from the USB interface100. However, in a USB device according to another embodiment of the invention illustrated inFIG. 4, a voltage regulator480is a part of a USB interface400. In this case, the voltage regulator480has a transistor482connected to a terminal voltage VDDand a resistor484positioned between the transistor482and a signal line250, as above-mentioned embodiment. Therefore, an operation of the voltage regulator480is similar to that of the voltage regulator200as shown in FIG.2. Further, the USB interface400according to another embodiment includes a basic memory410, a descriptor read/write portion420, a register430, a command analyzing portion440, a timer450, an initialization signal generator460and a USB core470. The elements of the USB interface400, except the voltage generator480, are similar to those of the USB interface100as shown in FIG.2. Therefore, the detailed description of the USB device according to another embodiment is omitted in this specification.

As described above, according to the USB device and the method for initializing the USB device of the invention, an additional memory applied to the conventional USB device is not required. Therefore, the USB device of the invention can considerably reduce the size and the manufacturing cost, as compared with the conventional USB device.

While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and equivalents may be made without departing from the spirit and scope of the invention. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.