JPS6151468B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a teletext receiving device in a so-called teletext service that multiplexes and broadcasts information signals during the vertical retrace period of a television signal (hereinafter sometimes simply referred to as a television signal). It is a thing,
More specifically, the present invention relates to a teletext receiver capable of receiving information signals multiplexed in a plurality of horizontal periods in a vertical retrace period.

Now, information signals converted into digital signals are multiplexed and transmitted during the vertical retrace period of the television signal, and the user can reproduce the screen composed of these information signals on a cathode ray tube as needed. Broadcasting services have recently been attracting attention as the next generation of information services. Devices that receive such teletext services generally use a microcomputer to perform processing such as decoding information signals and displaying them on a cathode ray tube. is sent at a high-speed pit rate of several megabits/second, so it is difficult to process this information signal directly in real time on a microcomputer.Therefore, a buffer memory is provided, and the sent information signal is processed in this buffer memory. After the data was recorded, a microcomputer read out the contents of this buffer memory, decoded it, and processed it. In Figure 1,
A block diagram of the above-mentioned conventional receiving device is shown. In FIG. 1, 1 is a video detection circuit, 2 is a synchronous separation circuit, 3 is a gate generation circuit, 4 is a clock generation circuit, 5 is a serial/parallel conversion circuit, 6 is an address counter circuit, 7 is an address switching circuit, and 8 is a The buffer memory includes a tuner that supplies signals to the video detection circuit 1, an IF circuit, a central processing unit that processes information signals written in the buffer memory 8, etc., which are not directly related to the explanation of the operation of this invention, and will therefore be omitted. There is.

FIG. 2 is a waveform diagram showing a waveform A of a television signal received by a conventional teletext receiving device and an output waveform B of a gate generation circuit in the device. In the figure, a indicates a vertical synchronizing pulse period, b indicates a horizontal synchronizing pulse, and c indicates an information signal multiplexed in the horizontal period.

Now, the receiving device shown in FIG. 1 receives an information signal multiplexed in one horizontal period of the vertical retrace period as shown in FIG. After separating only the synchronization signal from
A gate signal as shown in FIG. 2B is generated that gates only the horizontal period in which the information signal is multiplexed (however, the polarity is not necessarily as shown in FIG. 2B). On the other hand, the clock generation circuit 4 generates a clock signal synchronized with each bit of the information signal, and using this clock signal, the serial/parallel conversion circuit 5 converts the information signal into parallel data, and the address counter circuit 6 converts the information signal into parallel data. , this clock signal is counted to generate an address for the buffer memory 8 into which parallel data is to be written.
Then, using the gate signal described above, the address switching circuit 7 switches the address input terminal of the buffer memory 8 from the microcomputer side (not shown) to the output side of the address counter circuit 6 only during the horizontal period when the information signal is multiplexed. At the same time as connecting, the buffer memory 8 is put into a writing state,
The information signal is written into the buffer memory 8. However, in the conventional receiving apparatus, the information signals written in the buffer memory are limited to the information signals multiplexed in one horizontal period in the vertical retrace period, as shown in FIG. 2A. However, in this case, it takes time for the user to obtain the desired program after the user performs the program selection operation, and it also takes time for the screen to be completed, which can be very frustrating for the user. It is expected that there will be many cases. In order to eliminate this user's irritation, the teletext service is designed to provide not only one horizontal period in the vertical retrace period, but also multiple horizontal periods (as shown in FIG. 3A), for example.
indicates the case of two horizontal periods).
A method of multiplexing C ₁ and C ₂ has been proposed. However, as mentioned above, in conventional receiving devices, the information signals that can be received are limited to those multiplexed in one horizontal period of the vertical retrace period. It was impossible to receive information signals.

The present invention was made in order to solve the above-mentioned problems in the conventional receiving device, and therefore, an object of the present invention is to multiplex the vertical blanking period of a television signal into a plurality of horizontal periods. An object of the present invention is to provide a receiving device capable of receiving a plurality of information signals.

In order to achieve the above object, in the present invention, an address counter circuit that outputs an address at which an information signal is to be written to a buffer memory is divided into a first address counter circuit and a second address counter circuit. The first address counter circuit counts the clock signal output in synchronization with the information signal, and the second address counter circuit counts the number of horizontal periods in which the information signal is multiplexed. This allows multiplexed information signals to be recorded in the horizontal period of .

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a waveform diagram showing the waveform A of the television signal received by the teletext receiving apparatus according to the present invention and the output waveform B of the gate generating circuit in the apparatus.

FIG. 4 is a block diagram showing one embodiment of the present invention.

Please refer to FIGS. 3 and 4. The embodiment of the present invention shown in FIG. 4 differs from the conventional example shown in FIG.
The other symbols are the same as in the case of FIG. 1, and there is no change. Also,
In FIG. 4, the gate signal output from the gate generation circuit 3 is a signal that gates a plurality of horizontal periods. For example, as shown in FIG. 3A, information signals C ₁ and C ₂ are generated in two horizontal periods. In the case of multiplexing, a gate signal as shown in FIG. 3B (however, the polarity is not necessarily as shown in FIG. 3B) is output. The first address counter circuit 9 counts the clock signal output from the clock generation circuit 4 in synchronization with the information signal, and the output is sent to the buffer memory 8 during the horizontal period when the information signal is multiplexed by the address switching circuit 7. is connected to the lower bit terminal of the address. On the other hand, the second address counter circuit 10 counts the number of horizontal periods in which information signals are multiplexed, but for this purpose, as shown in FIG. Alternatively, a pulse obtained by detecting a synchronization code signal added to the beginning of the information signal may be used for counting. The output of the second address counter circuit 10 is connected by the address switching circuit 7 to the upper bit terminal of the address of the buffer memory during the horizontal period in which the information signals are multiplexed. Although not shown in FIG. 4, the buffer memory 8 is in a state in which data can be written only during the horizontal period in which information signals are multiplexed. With this configuration, the upper bits of the address of the buffer memory 8 are different in each of the plurality of horizontal periods in which the information signals are multiplexed, so that it is possible to write the information signals multiplexed in the plurality of horizontal periods to the buffer memory 8. It becomes possible.

Note that when the information signals to be multiplexed are in two horizontal periods, the second address counter circuit 10 is constituted by a set-reset flip-flop, and the output of the flip-flop is set in one horizontal period, and the output in the other horizontal period is set. It is clear from the above explanation that the output of the flip-flop should be in the reset state during the horizontal period.

As described above, according to the present invention, it is possible to realize a receiving device capable of receiving information signals multiplexed in a plurality of horizontal periods of a vertical retrace period, which was impossible to receive with conventional receiving devices. It has the advantage of being possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional teletext receiving device, and FIG. 2 shows a waveform A of a television signal received by the conventional receiving device and an output waveform B of a gate generation circuit in the device. FIG. 3 is a waveform diagram showing the waveform A of the television signal received by the receiving device of the present invention and the output waveform B of the gate generation circuit in the device, and FIG. FIG. 2 is a block diagram showing an embodiment. In the figure, 1 is a video detection circuit, 2 is a synchronous separation circuit, 3 is a gate generation circuit, 4 is a clock generation circuit, 5 is a serial/parallel conversion circuit, 6 is an address counter circuit, 7 is an address switching circuit, 8 is a buffer memory, 9 indicates a first address counter, and 10 indicates a second address counter.

Claims (1)

[Claims] 1. A teletext receiving device that receives information signals multiplexed and transmitted during the horizontal period of the vertical retrace period of a television signal, which comprises a buffer memory for storing the received information signal, and a buffer memory that is synchronized with the information signal. a first address counter that counts clock pulses output from the first address counter; a second address counter that counts the number of horizontal periods;
At the address specified by the output of the address counter and the output of the second address counter,
A teletext receiving apparatus comprising: means for writing an information signal into the buffer memory.