JPS6326184A - Teletext receiver - Google Patents

Abstract

PURPOSE:To surely extinguish a display element when the decoding of teletext is not executed by providing a circuit counting a horizontal synchronizing signal applying phase synchronization to the selfoscillation and a character multiplex reception display controlling circuit comprising a circuit initializing the counting circuit by a register output of an I/O port. CONSTITUTION:A counting circuit 304 counts up and overflows, and its output H goes to a H level for nearly 1sec, then a control signal J remains at the H level. Since a (n+4)th packet is a packet of an encoding transmission system, the counting circuit 304 is reset. If no character signal is inputted after the (n+1)th period, since a signal G resetting the counting circuit 304 remains at a L level, the output H of the counter circuit 304 goes to the H level after 1sec, one pulse is outputted at a reset output I, the control signal J of the display element goes to the L level and the display element extinguishes. Thus, the display element is not blinked in a short time by an operating signal and when the teletext is not received, the display element is surely extinguished.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a teletext receiver.

2. Description of the Related Art In recent years, teletext broadcasting, in which character signals are multiplexed during the vertical retrace period of television radio waves, has begun and has become widespread. Teletext broadcasts are not multiplexed and sent over the entire transmission time of television waves. Some broadcast stations do not provide teletext service.

Therefore, teletext receivers currently perform teletext broadcasting, and a display element or the like allows the user to recognize whether teletext broadcasting is possible.

An example of a teletext display indicating that a teletext broadcast is being performed in a conventional teletext receiver will be described below with reference to the drawings.

FIG. 4 is a block diagram showing the regeneration of the conventional text multiplex receiver.

In FIG. 4, 1 is a synchronization separation circuit, and the video signal A
Extract the horizontal sync signal and vertical sync signal. The horizontal synchronization signal is a phase-synchronized control of self-assisted oscillation using the horizontal synchronization signal of the broadcast wave extracted from the video, and when there is no signal, pulses are output by automatic oscillation. 2 is a waveform equalization single character signal separation circuit, 4 is a display clock generation circuit, 5 is a display control and bus control circuit, 6 is a color memory, 7 is a pattern memory, 8 is a color matrix circuit, 9 is an additional sound interface circuit, 10 is an additional sound decoder circuit, 11 is a microprocessor for character signal decoding processing (CPU chip 12 is a ROM for a program for character signal decoding processing, 13 is a work RAM, 14 is a buffer RAM, 15 is for code information and shiba turn information) Character generator for conversion, 1
6 is a keyboard for instructing program selection, etc.; 17 is a keyboard interface circuit for converting and connecting the signal input from the keyboard to the microprocessor in 11; and 18 is for switching between television signals and character signals. A switching circuit 19 is an I10 port consisting of a register for a microprocessor 11 to judge whether teletext broadcasting is being carried out and turns on a display element, and 20 is a display element and its driver.

A circuit for displaying that the teletext broadcasting receiver regenerated as described above is capable of receiving teletext will be described. From the video signal input, use the character signal separation circuit to extract the character signal from the waveform of 2 by gating the superimposed section of the character signal in the vertical blanking section with the output of the sync separation circuit 1.
Let it be a value signal.

This signal is sent to the error correction circuit 3, and errors occurring on the transmission path are corrected. The received data after this error correction is completed, 11 CPUs, 12 program ROMs, 13
Data processing is performed in a decoding processing section such as a work RAM of 14, a buffer RAM of 14, a character generator of 15, etc., and graphics and character information to be displayed are sent to the pattern memory of 6 color memories 7 via a display control circuit of 5. Decode and display the teletext screen by writing. The transmitted data relating to the additional sound is transferred to the sound duder circuit 1o via the additional sound interface 9, and the additional sound is decoded to generate sound. Conventionally, in order to determine that a teletext service is being provided and to display that teletext can be received, the data packet service is used to decode error-corrected received data. The microprocessor of 11 judges the identification (SI) and determines whether the pattern transmission method is a coded transmission method or an operational signal, and lights up or lights up the display element in the register of the I10 port of 19 in FIG. This was done by writing data to turn off the light.

Problems to be Solved by the Invention However, the above-mentioned regeneration has the following problems. Currently, when regenerating teletext programs, operational signals are sent to multiplexed packets, and operational signals are sometimes inserted to fill gaps in the program.

Therefore, the received data superimposed on the vertical retrace period is
When the microprocessor 1 determines the service identification (SI) for each vertical period and controls the I10 port, there is a period in which the light is turned off even though the teletext service is being provided for several vertical periods. In some cases, the display element would blink. FIG. 5 explains this state. D indicates a vertical synchronization signal, and E indicates a data packet superimposed on the direct return period. n is a packet with SI indicating the encoded transmission method, n+1 to n
+3 is a packet of the operational signal, and n+4 is a packet of the encoded transmission method. The microprocessor in FIG. 411 performs service identification (S
Since the 110 ports for display are controlled by determining I), the display element lights up from the arrival of data packet n to data packet n+1, turns off for data packets n+1 to n+3, and turns off at n+4. The light will turn on again and the display will blink.

Depending on the timing, when the antenna cable is disconnected or the video signal input is disconnected from an adapter-type text multiplex receiver, the display element may remain lit even though the text multiplex screen cannot be decoded. Something was happening.

The state and imaginary state are shown in Figure 5. If the video signal input is cut off due to a cable being disconnected at point X after taking in data packets n + 1, determining the SI, and performing the lighting process, the microprocessor will perform the determination process using an interrupt. It remains lit because it cannot be performed. F indicates a display element control signal from the I10 port.

In view of the above-mentioned problems, the present invention has a teletext reception display means that does not cause the display element to blink when a teletext service is being provided, and is turned off reliably when the teletext service cannot be received. The present invention provides a teletext receiver.

Means for Solving the Problems In order to solve the above problems, the present invention initializes a circuit that counts a horizontal synchronization signal obtained by applying phase synchronization to self-excited oscillation, and the counting circuit using a register output from the I10 port. It is equipped with a character multiplex reception display control circuit consisting of a circuit, an I10 port, a display element, and its driver circuit.

Operation The present invention allows the microprocessor to perform I1 by the above-mentioned regeneration.
Initialize the counting circuit for the horizontal synchronization signal through the 0 port, thereby turning on the display element, and turning it off by the output of the counting circuit when no teletext is received for a period of time set by the counting circuit. Therefore, the display element does not blink for a short time due to operation signals, etc., and it is possible to display a teletext broadcast reception in which the light is reliably turned off when the teletext cannot be received.

EXAMPLE An example of the present invention will be described below with reference to the drawings. FIG. 1 shows a block diagram of a teletext receiver according to the present invention. 7 to 204 are the same as the conventional example. 3o is a teletext broadcasting reception display control circuit, B is a horizontal synchronization signal, C
is the display clock. FIG. 2 is a detailed circuit example illustrating teletext reception display. 19 is an I10 port, which is made up of 191 flip-flops. K is the data line and L is the write pulse to the register.

3o is a teletext reception display control circuit, 304 is a counting circuit that counts horizontal synchronizing signal B, 301 and 302 are flip-flops that delay write pulses, and 303 is N
It is an OR circuit, and the output of the register and the gate of the delayed write pulse are connected to the reset signal G and the reset terminal of the counting circuit 304. 306,307+
7) A set-reset circuit is regenerated using a NOR circuit and a 7-lip flop 308, and one end of the NOR circuit 306 receives a reset signal G, which serves as a set signal for the above set-reset circuit. One end of 307 is 305
The output of the AND circuit is connected and serves as a reset signal for the set-reset circuit. 306 AND
The output H of the counting circuit and the horizontal synchronization signal B are input to the circuit.

The output J of 308 is connected to the base of the transistor 202 via the resistor 201. transistor 202
The emitter is grounded, and the collector is connected to the display element 204 via a resistor 203.

The operation of the character multiplex reception display circuit regenerated as described above will be explained with reference to FIG.

D and X are the same signals as explained in the conventional example.

11 Marocro Processor is a service for imported data.
Determine Ili (3 steps) and write IH/ to the register 191 of the I10 port of 19 at the time of data packet n, and the inverted output of 191 is a signal obtained by delaying the write pulse L by the NOR circuit of 303. It is gated and becomes a positive pulse like G in FIG. 3, which initializes the counting circuit 304. At the same time, the set/reset circuit is set to the control signal J for the display element using L.
is set to 'H' and the display element 204 is turned on. n+1～
Since the n+3 packet is an operational signal, it is registered in register 19.
Write 'L' to 1 and reset 7) Pulse G cannot be output enough. The counting circuit 304 counts up, but since the counting circuit overflows and its output H reaches ``H'' for about one second, J remains at ``H''. Since the n+4 packet is a coded transmission packet, the counting circuit is set. When no character signal is input after n+1, the signal G that resets the counting circuit is up to 1 of 'L', so after 1 second, the output H of the counting circuit jumps to 'H level' and the set reset circuit is reset. A pulse is output to the reset output of the display element, and the control signal J for the display element becomes LL level, causing the display element to turn off. Therefore, the display element does not blink for a short time due to the operation signal as in the conventional example, and can be surely turned off when teletext cannot be received.

Effects of the Invention As described above, the present invention provides a counting circuit for counting the regenerated horizontal synchronizing signal by applying phase synchronization with the horizontal synchronizing signal obtained by synchronously separating an input video signal to self-excited oscillation, and the counting circuit. , I1 in which a microprocessor for decoding teletext data determines the presence or absence of teletext and outputs the result.
By providing a teletext reception display circuit that resets when a teletext broadcast is being performed on the 0 port, even if a short-time operation signal packet is inserted following a coded transmission packet, the teletext transmission will continue. It is useful to be able to obtain a teletext broadcasting receiver having a teletext reception display means that does not cause the reception display display element to blink for a short period of time and turns off reliably when teletext cannot be decoded.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the regeneration of a text multiplex receiver in an embodiment of the present invention, FIG. 2 is a circuit diagram showing an embodiment of the text multiplex reception display control circuit, and FIG. 3 shows its operation. FIG. 4 is a block diagram of a conventional character multiplex receiver having a character multiplex reception display circuit, and FIG. 5 is a waveform diagram for explaining its operation. 19...I10 boat, 2o...Display element drive circuit, 30...Teletext broadcast reception display control circuit, 191...Register, 304...
...Counting circuit, 308...D flip-flop. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 p -++ + Ino. LLI Φ ヱ +-+h
Figure 4!

Claims (1)

[Claims] A counting circuit that counts the regenerated horizontal sync signal by applying phase synchronization to the horizontal sync signal obtained by synchronously separating the input video signal from self-excited oscillation, and a microprocessor that uses the counting circuit to decode teletext data. However, there is a circuit that determines the presence or absence of teletext based on the service identification code of the packet data and initializes it with the output from the output port that outputs the result, and a circuit that resets it with the output of the counting circuit and outputs the result from the output port. A teletext broadcasting system comprising: a set reset circuit for setting a teletext broadcast, and a teletext broadcast reception display circuit section that drives a display element with its output via a display element drive circuit to display a teletext broadcast reception display. Receiving machine.