JP2002297273A - Electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a USB interface circuit capable of improving convenience by making it unnecessary to replace a USB cable at the time of switching a device, and realizing space reduction and power consumption reduction at the time of providing a plurality of devices to be USB-connected in one device. SOLUTION: This video camera system 1 is provided with a memory card and a video camera arranged in one device as USB devices and one USB connector for USB connecting the device. At the time of switching the device to be USB-connected from the video camera to the memory card, the outputs of all USB transceivers are turned to be high impedance, and a transmission line is isolated from a voltage source, and the connection of the device before switching to a host 2 is released, and only the output of the USB transceiver of the switched device is validated, and the transmission line is pulled up, and the switched device is connected to a computer device 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a USB (Universa)
The present invention relates to an electronic device having a (Serial Bus) interface, and more particularly, to an electronic device having a plurality of USB-connected devices in one device.

[0002]

2. Description of the Related Art In recent years, a USB interface has been widely used for connecting a host device such as a personal computer and peripheral devices such as a printer and a video camera.

Some peripheral devices having such a USB interface include a plurality of devices that can be connected by USB in one device. For example, in a digital video camera with a built-in memory card drive, the host device can reproduce image data from a video tape by connecting the host device to the video camera via USB, and the host device can connect to the memory card drive via USB. By doing so, data can be recorded on and reproduced from the memory card.

[0004]

By the way, in the case of such a peripheral device having a plurality of USB devices in one device, the USB interface configuration is to provide a plurality of USB connectors corresponding to each device. Or one USB connector, but it is necessary to provide a HUB for distribution switching inside.

However, the configuration in which a plurality of USB connectors are provided requires a large space for attaching the connectors, and when switching the device to be connected to the host via USB, it is necessary to replace the USB cable with another USB connector. there were. Therefore, in such a configuration in which a plurality of USB connectors are provided, the usability when switching USB devices is very poor.

In a configuration in which a HUB is provided, it is not necessary to disconnect and connect the USB cable when switching the device to be connected to the USB.
This requires a space for incorporating the device, which results in an increase in the device configuration, an increase in power consumption, and an increase in cost.

[0007] The present invention has been made in view of such circumstances, and when a plurality of USB-connected devices are provided in one device, the USB is switched when the devices are switched.
USB that eliminates cable replacement, improves usability, and requires less space and lower power consumption
It is an object to provide an electronic device with a built-in interface.

[0008]

An electronic device according to the present invention is an electronic device connected to a host device via a serial interface conforming to the USB (Universal Serial Bus) standard. A plurality of devices capable of data transmission to and from each other, a plurality of transceivers provided corresponding to each device and serving as an input / output interface of each device, and a single cable connection between the host and the device. A connector, a transmission line for transmitting signals exchanged between the connector and the plurality of transceivers, a pull-up unit for pulling up the transmission line to a voltage source via a resistor, A selector for switching and selecting one device;
Control means for controlling the transceiver and the pull-up unit in accordance with the switching selection of the selection unit, wherein the control unit validates only the output of the transceiver corresponding to the device selected by the selection unit In addition, when the connection between the selected device and the host is performed in a state where the transmission line is pulled up and the device connected to the host is switched by the selection unit,
The outputs of all transceivers are set to high impedance, the transmission line is disconnected from the voltage source, the connection between the device before switching and the host is opened, the output of the transceiver of the device after switching is enabled, and the transmission line Is pulled up to make connection between the switched device and the host.

In this electronic device, a USB device is provided in one device.
A plurality of devices to be connected are provided, and when switching the connection device with the host, the outputs of all transceivers are set to high impedance, the transmission line is disconnected from the voltage source, and the connection between the device before switching and the host is changed. The connection is opened, the output of the transceiver of the device after the switching is made valid, and the transmission line is pulled up to connect the device after the switching to the host.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a video camera system with a built-in memory card drive to which the present invention is applied will be described as an embodiment of the present invention.

The video camera system according to the present embodiment
A camera-integrated video tape recorder (hereinafter simply referred to as a video camera), which is an imaging and image recording / reproducing device;
A memory card drive that writes and reads data to and from a memory card, which is a data recording device, is incorporated in one device. The video camera and the memory card drive are both devices (USB devices) connectable via USB, and are recognized as independent USB devices by host devices such as computer devices.

FIG. 1 shows a system configuration diagram of a video camera system 1 according to an embodiment of the present invention.

The video camera system 1 is connected to a computer device 2 serving as a host device via a USB cable 3 so that the video camera system 1
Data transfer according to the SB interface specification is performed. The video camera system 1 includes a video camera unit 11, a memory card drive unit 12, a video camera USB interface 13, a memory card USB interface 14, a USB connector 15,
It comprises a mode changeover switch 16 and a controller 17.

The video camera unit 11 is a unit provided with a video camera and a tape recorder. The video camera unit 11 has a recording function of recording image data and audio data taken and recorded on a video tape, and has a function of recording image data recorded on the video tape. And a playback function for playing back audio data.
When the video camera unit 11 is connected to the computer device 2 via USB, the computer device 2 can reproduce and read image data and audio data recorded on a video tape.

The memory card drive unit 12 has a memory card drive in which a memory card having a semiconductor memory is mounted and which writes and reads data to and from the mounted memory card. The memory card drive unit 12 records and reproduces compressed image data and audio data, or records and reproduces computer data other than image data and audio data, on a removable memory card. This memory card drive unit 12 is a video camera unit 1
1, image data and audio data captured and recorded can be converted into, for example, still image data and recorded. The memory card drive unit 12
Is connected to the computer device 2 by USB, the computer device 2 can write and read various data to and from the memory card.

Video camera USB interface 13
Performs data encoding / decoding and timing control in accordance with the USB interface specification, and transfers data between the computer device 2 and the video camera unit 11 connected via the USB cable 3.

Memory card USB interface 14
Performs data encoding / decoding and timing control according to the USB interface specification, and transfers data between the computer device 2 and the memory card drive unit 12 connected via the USB cable 3.

The USB connector 15 is a USB cable 3 which is a transmission cable conforming to the USB interface specification.
Are terminals to be connected.

The mode switch 16 is a switch operated by the user. This mode switch 1
Reference numeral 6 denotes a recording / reproduction mode of the memory card (memory mode), a recording mode by the video camera (camera mode), a power-off mode (off mode), and a reproduction mode of the image and audio data recorded on the tape (video mode). Perform switching.

In the memory mode, the video camera system 1 is recognized as a USB device as a memory card drive. That is, the video camera system 1 is set to this memory mode, and the computer device 2 and the USB
Once connected, the user can write and read data to and from the memory card by the computer device 2.

In the video mode, the video camera system 1 recognizes a USB device as a video camera. That is, when the video camera system 1 is set to the video mode and connected to the computer device 2 via USB, the user can reproduce the image data and the audio data recorded on the video tape by the computer device 2.

In the camera mode, photographing and recording using a video camera can be performed, and photographed image data and the like can be recorded on a video tape. In this camera mode, the video camera system 1 is not recognized as a USB device even if a USB connection is made to the computer device.

In the off mode, all functions are turned off.

The controller 17 controls the operation of each circuit of the system according to the mode position of the mode changeover switch 16.

Next, the USB connector 15 and each USB
The connection relationship with the interfaces 11 and 12 will be described.

In the video camera system 1, one USB device is connected to two USB devices (the video camera unit 11 and the memory card drive unit 12).
A connector (USB connector 15) is provided. In each of the USB interfaces 11 and 12, a USB transceiver is provided as a driver for input / output signals. USB in the video camera USB interface 13
Transceiver, USB transceiver 2 for video camera
1 and U in the memory card USB interface 14
The SB transceiver is a USB transceiver 22 for a memory card.

FIG. 2 shows the configurations of the video camera USB transceiver 21 and the memory card USB transceiver 22, and the connection relationship between these transceivers and the USB connector 15.

USB transceiver 21 for video camera
Is provided with a so-called three-state type output buffer 21a and an input buffer 21b having a function of setting the output impedance to infinity (high impedance). The output buffer 21a and the input buffer 21b each have two input terminals (a non-inverting input terminal (+ input terminal) and an inverting input terminal (-input terminal)) and two output terminals (a non-inverting output terminal (+ output terminal)). , Inverted output terminal (−
Output terminal)).

Output data is supplied from a functional block circuit in the memory card USB interface 13 to two input terminals of the output buffer 21a of the video camera USB transceiver 21. USB for video camera
Two output terminals of the input buffer 21b of the transceiver 21 supply input data to a functional block circuit in the memory card USB interface 13. Output buffer 2
The + output terminal of 1a and the + input terminal of the input buffer 21b are connected to the plus data terminal (D +) of the USB connector 15 via the plus line resistor R1. Further, the minus output terminal of the output buffer 21a and the minus input terminal of the input buffer 21b are connected via the minus line resistance R2 to the minus data terminal (D
-).

The memory card USB transceiver 22 is also provided with a so-called three-state output buffer 22a and an input buffer 22b having a function of making the output impedance infinite (high impedance). The output buffer 22a and the input buffer 22b each have two input terminals (a non-inverted input terminal (+ input terminal) and an inverted input terminal (-input terminal)) and two output terminals (a non-inverted output terminal (+ output terminal)). , Inverted output terminal (−
Output terminal)).

Output data is supplied from a functional block circuit in the memory card USB interface 14 to two input terminals of the output buffer 22a of the memory card USB transceiver 22. Two output terminals of the input buffer 22 b of the USB transceiver 22 for the memory card camera supply input data to a functional block circuit in the memory card USB interface 14. The + output terminal of the output buffer 22a and the + input terminal of the input buffer 22b are connected to the plus data terminal (D +) of the USB connector 15 via the plus line resistor R1. The minus output terminal of the output buffer 22a and the minus input terminal of the input buffer 22b are connected to the negative line resistance R.
2 is connected to the minus data terminal (D−) of the USB connector 15.

As described above, the USB transceiver 21 for the video camera and the USB transceiver 22 for the memory card are used.
Are connected in parallel to one USB connector 15.

The positive data terminal (D +) of the USB connector 15 is connected to a voltage source (VDD) via a pull-up resistor Rup and a pull-up switch 23. The plus data line to which the plus data terminal (D +) is connected is pulled up to the voltage source (VDD) when the pull-up switch 23 is turned on, and is opened when the pull-up switch 23 is turned off. When connecting a full-speed device specified in the USB interface specification, it is necessary to pull up the plus data terminal (D +) to the voltage source (VDD).
This is specified in the SB specification, and this example shows a circuit example when this high-speed device is connected. However, when connecting a low-speed device defined by the USB interface specification, pulling up the minus data terminal (D-) is defined by the USB specification. (D-) is pulled up.

Next, the operation of the USB connector 15 and the USB transceivers 21 and 22 having the above connection will be described.

A control signal A1 is supplied from the controller 17 to the video camera USB transceiver 21.
The video camera USB transceiver 21 switches between the outputs of the input buffer 21a and the output buffer 21b in a valid state or in a high impedance state according to the control signal A1. In addition, USB for memory card
The control signal A2 is supplied from the controller 17 to the transceiver 22. The memory card USB transceiver 22 switches between the outputs of the input buffer 22a and the output buffer 22b in a valid state or in a high impedance state according to the control signal A2. The pull-up switch 23 is switched by a control signal B from the controller 17.

When the mode switch 16 is set to the video mode, the controller 17 turns on the control signal A1 to enable the outputs of the output buffer 21a and the input buffer 21b of the video camera USB transceiver 21, and sets the control signal A2 to USB memory card as off
The output of the output buffer 22a and the input buffer 22b of the transceiver 22 are set to high impedance, and the control signal B
Is turned on and the pull-up switch 23 is turned on to pull up the data line.

When the computer 2 is connected via the USB cable 3 to the video camera system 1 in the video mode, the computer 2 can recognize the video camera system 1 as a video camera. That is, the computer device 11 recognizes only the video camera of the video camera system 1 as a USB device, and can reproduce video and audio data from the video tape attached to the video camera unit 11.

When the mode changeover switch 16 is set to the memory mode, the controller 17 turns off the control signal A1, sets the outputs of the output buffer 21a and the input buffer 21b of the video camera USB transceiver 21 to high impedance, and sets the control signal A2 Is turned on and the output buffer 22a of the USB transceiver 22 for the memory card is turned on.
Then, the output of the input buffer 22b is made valid, and the pull-up switch 23 is turned on to pull up the data line.

When connected via the USB cable 3 to the video camera system 1 in the memory mode, the computer device 2 can recognize the video camera system 1 as a memory card drive. That is, the computer device 11 recognizes only the memory card drive of the video camera system 1 as a USB device, and can record and reproduce data on the memory card mounted on the memory card drive unit 12.

When the mode changeover switch 16 is set to the off mode or the camera mode, the controller 17 controls the output buffer 21 of the video camera USB transceiver 21.
a, the output of the input buffer 21b is set to high impedance, the output of the output buffer 22a and the input buffer 22b of the memory card USB transceiver 22 is set to high impedance, and the pull-up switch 23 is turned off to open the data line.

Therefore, when the mode switch 16 is in the off mode or the camera mode, for example, the USB
Even if the cable 3 is connected, the computer device 2
Does not recognize both the video camera and the memory card drive of the video camera system 1 as USB devices.

Next, the user sets the mode switch 16
Is switched from the video mode to the memory mode.

First, the mode switch 16 is set to the video mode. At this time, the controller 17 outputs the output buffer 2 of the video camera USB transceiver 21.
1a and the output of the input buffer 21b are enabled, and the output buffer 22a of the USB transceiver 22 for the memory card is enabled.
The output of the input buffer 22b is set to high impedance, and the pull-up switch 23 is turned on to pull up the positive transmission line to a voltage source. Therefore, the computer 2 recognizes the video camera system 1 as a video camera.

In this state, when the user switches the mode switch 16 from the video mode to the memory mode, the controller 17 first turns off the control signal A1 and sets the output buffer 21a and the input buffer 21a of the video camera USB transceiver 21. The output of 21b is set to high impedance. That is, the outputs of the output buffers and input buffers of all USB transceivers are set to high impedance.

Subsequently, the controller 17 outputs the control signal B
Is turned off, and the pull-up switch 23 is opened. That is, the pull-up of the plus side transmission line is released.

In this state, the video camera unit 11 recognized as a USB device is released from the computer device 2.

Subsequently, the controller 17 outputs the control signal A
2 on, USB transceiver 2 for memory card
The output of the second output buffer 22a and the output of the input buffer 22b are made valid.

Subsequently, the controller 17 outputs the control signal B
Is turned on, and a pull-up switch 23 is connected.
That is, the plus transmission line is pulled up to the voltage source.

In this state, the memory card drive unit 12 is recognized by the computer device 2 as a USB device.

As described above, in the video camera system 1 according to the embodiment of the present invention, a plurality of devices connected by USB are provided in one device, and the computer device 2
When switching the USB device to be connected to the device, for example, when switching the device to be connected to the USB from the video camera to the memory card drive, the output of each USB transceiver is set to high impedance, the transmission line is disconnected from the voltage source, and the device before switching is connected. The connection between the switching device and the computer device 2 is released by enabling the output of the USB transceiver of the device after switching and pulling up the transmission line.
Make a connection with

As a result, in the video camera system 1, the device connected to the computer device 2 can be switched without replacing the USB cable when switching the device. Therefore, an interface that is easy for the user to use can be provided. Also, H
Switching between a plurality of USB devices can be realized with a very simple configuration without providing a data distribution device such as a UB inside.

Although the embodiment of the present invention has been described above with respect to a video camera device with a built-in memory card to which the present invention is applied, the present invention is not limited to a video camera device, but includes a plurality of USB devices. May be applied to any electronic device provided in one device.

[0053]

In the electronic apparatus according to the present invention, a plurality of USB-connected devices are provided in one device, and when switching the device connected to the host, the outputs of all transceivers are set to high impedance. And disconnect the transmission line from the voltage source, open the connection between the device before switching and the host, enable the transceiver output of the device after switching and pull up the transmission line, and connect the device and host after switching. Is connected to

Thus, in the electronic apparatus according to the present invention, the device connected to the host can be switched without replacing the USB cable when switching the device. Therefore, an interface that is easy for the user to use can be provided. Further, the electronic apparatus according to the present invention can realize switching of a plurality of USB devices with a very simple configuration without providing a data distribution device such as a HUB inside. Therefore, the electronic device according to the present invention can configure a system with a small space and low power consumption.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a video camera system according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a USB transceiver and a connection relationship between the USB transceiver and a USB connector.

[Explanation of symbols]

1 video camera system, 2 computer device, 3
USB cable, 11 Video camera unit, 12
Memory card drive unit, 13 video camera USB interface, 14 memory card USB interface, 15 USB connector, 21 USB transceiver for video camera, 22 USB for memory card
Transceiver, 23 pull-up switch

Claims (1)

[Claims] 1. An electronic device connected to a host device via a serial interface conforming to a USB (Universal Serial Bus) standard, comprising: a plurality of devices capable of transmitting data with the host via the USB; A plurality of transceivers provided for each device and serving as an input / output interface of each device; one connector for connecting a cable between the host and the apparatus; and a plurality of transceivers between the connector and the plurality of transceivers A transmission line for transmitting an exchanged signal; a pull-up unit for pulling up the transmission line to a voltage source via a resistor; a selection unit for switching and selecting one of the plurality of devices; And control means for controlling the transceiver and the pull-up unit in accordance with the switching selection of: While only the output of the transceiver corresponding to the device selected by the selection unit is enabled and the transmission line is pulled up, a connection is made between the selected device and the host, and the selection unit When the device connected to the host is switched, the outputs of all transceivers are set to high impedance, the transmission line is disconnected from the voltage source, the connection between the device before switching and the host is opened, and the device after switching is switched. An electronic device that enables the output of the transceiver of (1) and pulls up the transmission line to connect the device after switching to the host.