JPS58156279A - Character broadcasting receiver - Google Patents

Abstract

PURPOSE:To always use the display of a CRT to the display on a TV screen, by applying the resetting or interruption to a CPU with a pulse signal produced from a channel selecting device when the TV channels are selected. CONSTITUTION:A voice muting signal line 7 is connected to a resetting circuit 20. A CPU10 is reset by a voice muting signal delivered from a channel selecting device 2 oven in case the channels are selected through a channel selecting keyboard 3. As a result, a signal switch circuit 17 selects a TV screen, i.e., the output of an amplifying/color demodulating circuit 5 with a resetting process of the CPU10. Thus the display of a CRT is always identical to the display on the TV screen.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a teletext receiver capable of receiving a character signal multiplexed with a television signal and displaying a character graphic screen.

A character signal converted into a digital signal is multiplexed and transmitted during a portion of the vertical blanking period of the television signal, and the user can display a character graphic screen composed of this character signal on the receiver's cathode ray tube as needed. Recently, teletext services that can provide information have been attracting attention as next-generation information services.

FIG. 1 shows a block diagram of a conventional teletext receiver capable of receiving such teletext services.

In Figure 1, 1 is a tuner, and 2 is a channel selection device.

3 is the tuning keyboard, 4 is the IF/detection circuit, and 5 is the amplification/detection circuit.
6 is an audio detection/amplification circuit; 7 is an audio mute signal line; and 8 is a signal extraction circuit.

9 is a buffer memory, 10 is a central processing unit (C
11 is a read-only memory (hereinafter abbreviated as ROM), 12 is a keyboard, 16 is a keyboard interface circuit, 14 is a display memory 15 is a display memory reading circuit, and 16 is a signal conversion circuit.

17 is a signal switching circuit, 18 is an address /( bus, 19 is a data bus, 20 is a reset circuit, 21 is a reset signal line, 22 is an interrupt identification circuit, and 23 is an interrupt signal line).

In FIG. 1, tuner 1. Channel selection device 2゜Tuition selection keyboard 3. IF/detection circuit 4. Amplification/color demodulation circuit5. The audio detection/amplification circuit 6 and the audio mute signal line 7 are the same as those used in ordinary television receivers, and their operation is well known, so a detailed explanation will be omitted. In order to suppress the temporary audio noise when the channel is switched, an audio detection/amplification circuit is used to generate a pulse signal for so-called audio muting, such as cutting off the audio or lowering the audio level while the channel is being switched. 6.

Note that this audio mute signal is supplied to the amplification/color demodulation circuit 5, as shown by the dotted line in Figure 1, and the TV is turned off during channel switching to avoid displaying a distorted screen when switching channels. Although they may be used for purposes other than audio muting, such as temporarily erasing a picture, in the description of the present invention, these will be collectively referred to as audio muting signals for convenience.

Now, in FIG. 1, the parts other than the circuit part for receiving and displaying the television signal mentioned above, that is, the parts numbered after 8 in FIG. 1, are for receiving teletext. C according to the processing program recorded in
P Ulo processes character signals recorded in the buffer memory 9 or key data input from the keyboard 12 . That is, the CPU 10 decodes the character signals extracted from the television signal field by field and written into the buffer memory 9, and determines the program number that matches the program number of the teletext broadcast that the user inputs from the keyboard 12 and requests to receive. The pattern data and the like of the character signals are written into the display memory 14. The display memory reading circuit 15 reads out the contents of the display memory 14 in synchronization with the beam scanning of a cathode ray tube (not shown) in order to display teletext.The read data is read out by the signal conversion circuit 16.
It is converted into a signal suitable for display on a cathode ray tube. The signal switching circuit 17 selects and displays either the television screen output from the amplification/color demodulation circuit 5 or the character/figure screen output from the signal switching circuit 16 as the screen to be displayed on the cathode ray tube, or selects and displays both. It is used to switch signals such as super-displaying a text and graphics screen on the TV screen by mixing the signals, and the screen to be displayed is selected according to instructions from the keyboard 12 or a control code in the text signal that specifies the display mode. This is what is displayed on a cathode ray tube.

Note that the processing of character signals recorded in the buffer memory 9 or the processing of key data input from the keyboard 12 is designed as interrupt processing in the case of FIG. An interrupt signal is applied to cPUlo through an interrupt identification circuit 22 that can identify from which of the keyboard 12 and the keyboard 12 the interrupt signal is generated. Further, the reset circuit 20 generates a reset pulse when the power is turned on or when a reset key is pressed, and
10 performs a reset process, that is, initial settings for teletext reception, and causes the signal switching circuit 17 to select the television screen that is the output of the amplification/color demodulation circuit 5 in order to put the receiver in a television display state. It is. Note that the reset key is normally provided separately from the keyboard 12, but for convenience, it is included in the keyboard 12 as the first reset key.
In the figure, the keyboard 12 and the reset circuit 20 are connected.

Now, in this conventional teletext receiver shown in FIG. 1, the keyboard 12 for selecting teletext programs is a CP
On the other hand, the channel selection keyboard 3 that selects the TV channel only drives the channel selection device 2 to set the channel of the TV broadcast program that the tuner 1 receives, and the processing is performed by the CPU 10. has nothing to do with it at all. Therefore, this conventional teletext receiver had the following drawbacks.

In other words, if you have received a TV teletext program on a certain channel and are displaying it on the CRT, and you want to watch TV on another channel, you cannot simply select that channel using the channel selection keyboard 3. , the TV screen is not displayed, and the TV teletext screen of the previous channel is still displayed. Therefore, in such a case, it is necessary to operate the channel selection keychain 3 and then operate the key for selecting the TV screen or the reset key from the keyboard 12 (however, if you operate the keyboard 12 first, It was possible to operate the channel selection keyboard 3 from the ridge), but the operability was very poor. In addition, if you only operate the TV channel selection keyboard 5 but forget to operate the keys to select the TV screen from the keyboard 12, the newly selected channel will be displayed on the TV.
If a teletext broadcast with the same program number as the teletext broadcast received and displayed on the previous channel is being transmitted, the teletext broadcast on the new channel with completely different content will be displayed following the previously received teletext broadcast. Since teletext is received and displayed, users may be under the illusion that the historical broadcasting receiver is malfunctioning and may request repairs.

An object of the present invention is to eliminate the above-mentioned drawbacks of the conventional teletext receiver, and even if teletext is being received and displayed, if a key operation is performed on the channel selection keyboard, the CRT receiver The object of the present invention is to provide a teletext receiver in which the display of the selected channel automatically changes to the television screen of the selected channel.

According to the present invention, when a TV channel is selected,
Focusing on pulse signals generated by the channel selection device, such as audio mute signals, this pulse signal is used to reset or interrupt the CPU, and when a channel selection operation is performed, the CPU changes the display screen. can be switched to a TV screen.

Hereinafter, the present invention will be explained in detail using the drawings. FIG. 2 is a block diagram showing an embodiment of the present invention. Each component in FIG. 2 is the same as in FIG. 1, and the points different from FIG. 1 are as follows.
According to the present invention, the audio mute signal @7 is transmitted to the reset circuit 20.
is connected to.

That is, in the teletext receiver shown in FIG. 2, the CPU 10 is reset not only when the power is turned on or when the reset key is pressed, as in the conventional case, but also when a channel is selected from the channel selection keyboard 3. Even when an operation is performed, the audio mute signal output from the channel selection device 2 at that time! R, C
PUjOi/(IJ is set, and as a result cPU1
By the reset process of o, the signal switching circuit 17 selects the television screen which is the output of the amplification/color demodulation circuit 5, so that the display on the cathode ray tube always becomes the television display. As for the specific method of connecting the audio mute signal line 7 and the reset circuit 2o according to the present invention shown in FIG. 2, various methods can be considered depending on the polarity and level of the pulse of the audio mute signal and the system of the reset circuit.

FIG. 3 shows a specific example of the connection between the audio mute signal line 7 and the reset circuit 2o when the audio mute signal is a positive pulse. 24°26, 31.32.5 in Figure 3
4 are resistors, 25 are capacitors, 27 are diodes, 28 and 29 are inverters, and 30 is a reset key (included in the keyboard 12 in Figures 1 and 2).
, 33 is the main power supply voltage terminal of the transistor 55, and the other symbols are the same as in FIG. Note that the main power supply voltage terminals 35 are actually connected to the inverters 28, 29, . C.P.
Although it is connected to a power supply voltage terminal such as Ulo, it is omitted in FIG.

When power is turned on or reset key 3 in this figure 3.
The operation when 0 is pressed is well known, so a description thereof will be omitted. In Fig. 3, when a channel selection operation is performed, a positive pulse is output to the audio mute signal line 7, so
This positive pulse causes the transistor 33 to conduct in a saturated state, and the voltage of the inverter 280 becomes lower than the threshold voltage of the inverter 28, and the reset pulse is applied to the CPU.
10.

Note that the resistor 34 shown in FIG. 3 may not be necessary in principle, but is used to limit the discharge current of the capacitor 25, and is selected to have a value sufficiently smaller than that of the resistor 24.

Further, the resistor 32 may also be omitted. As mentioned above, various methods can be considered for connecting the audio mute signal line 7 and the reset circuit 20, and in FIG.
It is also possible to connect the collector of the transistor 33 directly to the output of the inverter 29, ie, the reset signal @21, instead of the input of the inverter 28, by connecting a resistor between them.

(In this case, the resistor 64 is unnecessary.) The inverter 29 is configured with a two-way NOR circuit, the collector of the transistor 33 is connected to the main power supply voltage terminal 35, and a resistor is connected between the emitter and ground. Various methods can be considered, such as connecting one input of the two-power NOR circuit to the output of the inverter 28, and the other input to the emitter of the transistor 5S, which is connected differently from that in FIG. 3 according to the above.

Also, when the audio mute signal is a negative pulse, there are various ways to connect the audio mute signal line 7 and the reset circuit 20 depending on the negative pulse. However, the present invention does not require a specific connection method. In the example shown in FIG. 2, the pulse width of the reset signal applied to the CPU Ulo at the time of channel selection is the same as the pulse width of the audio mute signal. However, the pulse width of the audio mute signal is usually selected to be on the order of several hundred milliseconds. Furthermore, the C P Ulo enters the reset process from the time when the applied reset signal is no longer present. Therefore, in the case of FIG. 2, there is a slight time difference between when the channel selection operation is performed and when the CPU 10 performs the reset process. During this period, when triggered by the leading edge of the audio mute signal pulse, outputs a pulse that is sufficiently short compared to the audio mute signal pulse width (but longer than the pulse width of the reset pulse required for CPU1o). A monostable multivibrator or the like may be inserted.

In addition, in the embodiment of FIG. 2, the audio mute signal
Although P Ulo is reset, it is clear that the process for switching the cathode ray tube display to the television screen at the time of channel selection is not limited to the reset process, but may also be an interrupt process. Therefore, when an interrupt occurs due to the audio mute signal, an interrupt processing program that stops the reception of the teletext and changes the CRT display to the TV screen is stored in the ROM 1, and the audio mute signal line 7 is It may also be connected to the interrupt identification circuit 22. Also C
If the PU10 has two or more types of interrupt terminals and there is an unused interrupt terminal, connect the audio mute signal line 7 directly or after converting its polarity, level, etc., to the interrupt terminal of that CP Ulo. It is clear that it may be connected to

In addition, when selecting a channel, in order to switch the CRT display to the TV display, the audio mute signal is used to switch the CP Ulo
An interrupt processing board is provided which is set by the voice output signal without resetting or interrupting the field. When this I/Q port is set to refer to the I10 port, the I/Q port with 1 may be reset by switching the CRT display to the TV display, or the audio mute signal If the pulse width is longer than the field period, an audio mute pulse is generated by referring to the audio mute signal during interrupt processing performed for each field through a simple I/Q port. It is obvious that the display on the cathode ray tube may be switched to the TV display when the TV is in use.0Also, most of the processing for displaying the teletext reception 9 in Fig. 2 is software processing and is stored in the ROM 11. Although the CPU 10 performs the processing according to a loaded processing program, there are also teletext receivers that do not use the CPU 10 and process everything by hardware, and it is clear that the present invention can be applied to these as well. be.

Furthermore, the present invention is not limited to a teletext receiver, but also applies to a device that can display a text and graphic screen in addition to a television using a television receiver, for example, a terminal for text and graphic information service using a public telephone line. It is obvious that the present invention can be similarly applied to machines, home computers, etc.

In addition, in FIG. 2, an audio mute signal is used as a pulse signal to reset the CP Ulo, but this pulse signal is not limited to the audio mute signal. It is clear that the pulse signal output from the tuning keyboard 3 may be used to drive the device 2, or a pulse signal other than the audio mute signal generated in the tuning device 2 at that time may be used. It is also obvious that a circuit for directly detecting the pressing of a key may be added to the channel selection keyboard 5 to reset the CPU Ulo.

As described above, according to the present invention, when a TV channel is selected, the display on the cathode ray tube always becomes the display on the TV screen.
If a channel is selected while a teletext screen is being displayed, there is no need to perform an additional TV selection operation, and operability can be greatly improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional teletext receiver, Figure 2 is a block diagram showing a conventional teletext receiver.
The figure is a block diagram showing one embodiment of the present invention, and FIG.
FIG. 2 is a circuit connection diagram specifically showing main parts of the circuit shown in the figure. Code explanation

Claims (1)

[Scope of Claims] 1) In addition to being equipped with a channel selection device and a tuner and capable of receiving television signals and displaying them on a television, it is also equipped with a central processing unit (hereinafter abbreviated as CPU) to display characters multiplexed on the television signal. In a teletext receiver that can extract the signal and display it as a text/graphics screen, when a TV channel selection operation is performed, the screen changes to the TV display even if the text/graphics screen is being displayed. A teletext receiver comprising means for outputting a setting signal to the CPU so as to switch the CPU. 2. The teletext receiver according to claim 1, wherein the setting signal is a mute signal that is generated in the channel selection device only when a channel selection operation is performed. Broadcast receiver.