JPH04286281A - Input/output circuit - Google Patents

Abstract

PURPOSE:To enable a single input/output terminal to be selectively used for inputting or outputting in a input/output circuit. CONSTITUTION:The single input/output terminal (7) is provided and also an input/output changing-over switch (8) which selects the input/output terminal (7) as one for inputting a video signal or one for outputting is provided. When the input/output terminal (7) is used as a video input terminal, the input/output changing-over switch (8) is changed-over to the side of a contact point (A) and when it is used as a video output terminal, the input/output changing-over switch is changed-over to the side of the contact point B.

Description

[Detailed description of the invention]

0010

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input/output circuit for video or audio signals used in video equipment, audio equipment, etc.

[0020]

2. Description of the Related Art Conventionally, for example, a video signal input/output circuit of a television receiver is configured as shown in FIG.
(1) is a video input terminal to which a connection cord for input from an external video device (for example, a video tape recorder, etc.) is connected and the video signal (in this case, a composite video signal) is input; 2), for example, switches between the video signal from the video input terminal (1) via the input buffer circuit (3) for impedance matching and the video signal extracted by video detection from the received signal of the internal receiving circuit. The selection is made based on the signal (for example, the AV switching signal output from the control microcomputer of the receiver to automatically switch the TV screen to the video screen when the video tape recorder is activated). A video switching circuit (4) outputs the video signal derived from the video switching circuit (2) to a video processing circuit (not shown), for example, an output buffer circuit (5) for impedance matching.
), and a connection cord for output to the external video device is connected to this video output terminal (4). Therefore, the video switching circuit (2
The video signal from the video input terminal (1) or the receiving circuit selected in ) is led to the video processing circuit, and at the same time is outputted from the video output terminal (4) to external video equipment. Also, instead of the video output terminal (4) in FIG. 6, another video input terminal (6) is provided individually as shown in FIG. 7 and connected to the input side of the input buffer circuit (5), so that one video input There is also a device in which the video signal input to the terminal (1) is output from the other video input terminal (6).

[0030]

[Problem to be Solved by the Invention] However, in the former case, in the input/output circuit with the conventional configuration, since dedicated video input terminals and video output terminals are provided respectively, the number of components increases. This increases the installation space in the terminal installation section of the receiver, which hinders miniaturization. Furthermore,
When connecting a connection cord from an external video device, it was necessary to confirm whether it was for input or output, resulting in poor operability. Furthermore, in the latter case, it is necessary to provide two video input terminals for use as input or output, which similarly causes an increase in the installation space in the terminal installation section of the receiver. The present invention has been made in view of these points, and it is an object of the present invention to provide an input/output circuit that can save space in a terminal arrangement section and improve its operability.

[0040]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a single input/output terminal that is selectively used for input or output in an input/output circuit that inputs or outputs a signal. In addition, selection means for selecting the input/output terminal as input or output is provided. Specifically, when the input/output terminal is selectively used for inputting or outputting a video signal, the selection means is used to determine whether or not an external video signal is input to the input/output terminal. A determination circuit that determines the presence or absence of a synchronization signal included in the signal, and based on the determination result of this determination circuit, an external video signal is input from the input/output terminal, or an internal video signal is input from the input/output terminal. When the input/output terminal is selectively used for inputting or outputting an audio signal, the selection means is configured to select whether to output an audio signal from the outside. A determination circuit that determines whether or not a video signal is input based on the presence or absence of the signal level or signal frequency on the input/output terminal side, and an external audio signal from the input/output terminal based on the determination result of this determination circuit. It is configured with an input/output switching circuit that selects whether to input the audio signal or to output the internal audio signal from the input/output terminal.

[0050]

[Operation] According to such a configuration, a single input/output terminal is selectively used for inputting or outputting a video or audio signal, and the selection is determined by whether the input/output terminal is used for inputting or outputting a video or audio signal. The determination circuit determines whether or not there is a synchronizing signal on the input/output terminal side, the signal level, and the signal frequency, and the input/output switching circuit automatically determines whether or not the signal is input based on the determination result. That will happen.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. It should be noted that the same parts as those in the prior art will be given the same reference numerals and the explanation thereof will be omitted. In this embodiment, a single input/output terminal is used for inputting video or audio signals input from an external device, not only in the case of a television receiver, but also because there is almost no need to output them to the outside at the same time as the input. It is designed to be used selectively for use or for output. Specifically, as shown in FIG. 1, a single input/output terminal (7) is provided, and an input/output switch (8) is provided to select the input/output terminal (7) for inputting or outputting a video signal. It has been established. With this configuration, when the input/output selector switch (8) is switched to the contact A side, the input/output terminal (7) is used as a video input terminal, and the input/output terminal (7) receives input from external video equipment. The video signal is input to the video switching circuit (2) via the input buffer circuit (3), and the video switching circuit (2) receives the video signal from this input/output terminal (7) or from the internal receiving circuit. One of the video signals is selected and output to the video processing circuit. When the input/output switch (8) is switched to the contact B side, the input/output terminal (7) is used as a video output terminal, and the video signal from the receiving circuit selected by the video switching circuit (2) is It is led out to the subsequent video processing circuit, and is also connected to the input/output terminal (7) via the output buffer circuit (5).
will be output to external video equipment. In addition, in Figure 1, the output buffer circuit (
However, as shown by the dotted line in Figure 1, the input/output terminal ( 7
) may be derived.

In addition, in FIG. 1, the input/output changeover switch (8)
However, if it is necessary to display a video signal from an external video device while a normal television receiver is displaying a video signal from the internal receiving circuit, Similarly, there are almost no cases where it is necessary to display a video signal from the internal receiving circuit when displaying a video signal from an external video device, so the input/output switching circuit (9 )
This input/output switching circuit (9) is operated based on the AV switching signal output from the receiver's control microcomputer to switch between the video signal from the receiving circuit and the video signal from the external video equipment. It may be possible to switch automatically. With this configuration, when the video switching circuit (2) selects the video signal from the internal receiving circuit based on the AV switching signal, the input/output switching circuit (9) switches the input/output terminal (7) to the output buffer circuit ( It is automatically connected to the output side of the input/output circuit (5) and used as a video output terminal, and conversely, when the video switching circuit (2) selects an external video signal by the AV switching signal, it is connected to the output side of the input/output circuit (2). 9), the input/output terminal (7) is automatically connected to the input side of the input buffer circuit (3) and is used as a video input terminal from an external video device.

In addition, as shown in FIG. 3, the input/output switching circuit (
9) Input the video signal from the input/output terminal (7) and the video signal from the internal receiving circuit, and switch to this input/output switching circuit (9).
A first synchronization separation circuit (10) inputs the output from the receiver circuit to the video switching circuit (2) and separates the synchronization signal from the video signal from the receiving circuit, and an external video device is connected to the input/output terminal (7). The second sync separation circuit (11) separates the sync signal from the video signal input from the input/output terminal (7) depending on the presence or absence of the sync signal from the first and second sync separation circuits (10) and (11). A synchronization determination circuit (12) that determines whether or not an external video signal is input is provided, and based on the determination result of the synchronization determination circuit (12), an input/output switching circuit (9) and a video switching circuit are provided. (2) may be automatically switched. With this configuration, when there is no synchronization signal from the second synchronization separation circuit (11), the synchronization determination circuit (12) determines whether the video signal from the external video device is input to the input/output terminal (7). The input/output switching circuit (9) is switched to a state where the video signal from the internal receiving circuit is output to the input/output terminal (7), and the video switching circuit (2) is switched to the state where the video signal from the internal receiving circuit is output. When switched to the selected state, the video signal from the receiving circuit is outputted to the external video equipment from the input/output terminal (7) used as the video output terminal, and is also led to the subsequent video processing circuit. Furthermore, when there is a synchronization signal from the second synchronization separation circuit (11), the synchronization determination circuit (12) detects the input/output terminal (
7) determines that a video signal from an external video device is being input, and sets the input/output switching circuit (9) to a state in which the video signal from the input/output terminal (7) is output to the video switching circuit (2). At the same time, the video switching circuit (2) is connected to the input/output terminal (7).
), and the video signal from the input/output terminal (7) used as the video input terminal is led to the subsequent video processing circuit. Then, when there is a synchronization signal from the second synchronization separation circuit (11) and there is a synchronization signal from the first synchronization separation circuit (10), the synchronization determination circuit (12) determines the priority order,
In this case, it is determined that the display of the video signal from the external video device has priority, and the input/output switching circuit (9) is switched to a state in which the video signal from the input/output terminal (7) is output to the video switching circuit (2). Connect the video switching circuit (2) to the input/output terminal (7
), and the video signal from the input/output terminal (7) used as the video input terminal is led to the subsequent video processing circuit. Also,
Here, the video switching circuit (2) and the input/output switching circuit (9) are automatically switched in conjunction based on the judgment result from the synchronization judgment circuit (12), but the video switching circuit (2)
) may be switched based on another AV switching signal, regardless of the judgment result from the synchronization judgment circuit (12). Although the video signal input/output circuit has been described in this embodiment, it may also be an audio signal input/output circuit, or both may be switched in conjunction.For example, an audio signal input/output circuit may be used. In this case, as shown in FIG. 4 or 5, the signal level or signal frequency (
A level or frequency determination circuit (13) or (14) is provided for determining whether or not an external video signal is input to the input/output terminal (7) based on the presence or absence of a video signal (which may be limited to a specific frequency); This judgment circuit (13) or (14)
The input/output switching circuit (9) and the audio switching circuit (15) may be automatically switched based on the determination result in step. For example, as in the case of video signals, the input/output terminal (7)
If there is no signal level or signal frequency from the side, the level or frequency judgment circuit (13) or (14) connects the input/output terminal (7) to external video equipment (or external audio equipment).
The input/output switching circuit (9) is switched to a state in which the audio signal from the internal receiving circuit is outputted to the input/output terminal (7), and the audio switching circuit (15) is switched to a state in which the audio signal from the internal receiving circuit is selected, and the audio signal from the receiving circuit is output from the input/output terminal (7) used as the audio output terminal to the external video equipment (or external audio equipment), It will be led out to the subsequent audio processing circuit. Note that, as in the case of the video switching circuit (2) described above, the audio switching circuit (15) is a level or frequency determining circuit (13).
Alternatively, the switching may be performed based on another AV switching signal, regardless of the determination result in (14).

[0090]

Effects of the Invention As described above, according to the input/output circuit of the present invention, a single input/output terminal is selectively used for input or output. The installation space in the terminal arrangement section can be reduced, and the connection cord from external video equipment can be reduced.
Since there is no need to check whether the card is for input or output when connecting, it is possible to downsize the receiver body and improve operability.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a block circuit in a video signal of the present invention.

FIG. 2 is a diagram showing other block circuit examples.

FIG. 3 is a diagram showing other block circuit examples.

FIG. 4 is a diagram showing an example of a block circuit for an audio signal according to the present invention.

FIG. 5 is a diagram showing other block circuit examples.

FIG. 6 is a diagram showing an example of a conventional block circuit.

FIG. 7 is a diagram showing other block circuit examples.

[Explanation of symbols] 2 Video switching circuit 7 Input/output terminal 8 Input/output switch 9 Input/output switching circuits 10, 11 First and second synchronization separation circuits 12 Synchronization determination circuit 13 Level determination circuit 14 Frequency determination circuit

Claims (4)

[Claims] 1. An input/output circuit for inputting or outputting signals, characterized in that the input/output circuit is provided with a single input/output terminal that is selectively used for input or output. 2. The input/output circuit according to claim 1, further comprising selection means for selecting the input/output terminal as one for input or one for output. 3. The input/output terminal is selectively used for inputting or outputting a video signal, and the selection means includes:
A determination circuit that determines whether an external video signal is input to an input/output terminal based on the presence or absence of a synchronization signal included in the signal, and a determination circuit that determines whether an external video signal is input to an input/output terminal based on the presence or absence of a synchronization signal included in the signal. 3. The input/output circuit according to claim 2, further comprising an input/output switching circuit for selecting whether to input the video signal from the input/output terminal or to output the video signal from the inside from the input/output terminal. 4. The input/output terminal is selectively used for inputting or outputting audio signals, and the selecting means includes:
A determination circuit that determines whether or not an external audio signal is input to the input/output terminal based on the presence or absence of a signal level or signal frequency on the input/output terminal side; 3. The input/output circuit according to claim 2, further comprising an input/output switching circuit for selecting whether to input an audio signal from the input/output terminal or to output an internal audio signal from the input/output terminal.