JPH08149330A - Television signal processing ic - Google Patents

Abstract

PURPOSE: To designate a vertical blanking period suitable for a receiver. CONSTITUTION: This IC is an IC used to generate a video signal from a television signal received by a television receiver and provided with a designation input pin 102 used to designate a vertical blanking period corresponding to a vertical blanking period of a television receiver and a vertical blanking pulse generating section 106 generating a desired vertical blanking period according to the designation by a designation means. The vertical blanking period suitable for the receiver is designated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal processing IC, and more particularly to an improved television signal processing IC which generates a vertical blanking period corresponding to a vertical blanking period of a television receiver. .

[0002]

2. Description of the Related Art When reproducing an image on a television receiver, the fluorescent screen of a cathode ray tube is continuously scanned by an electron beam. For example, NTSC adopted in Japan
Considering the method, one frame is composed of two fields, and each field has a number of scans of 262.5. That is, 2 in the first 1 field
Rough scanning is performed from the upper end to the lower end of the screen with 62.5 scanning lines, and 262.
One frame is completed by filling with 5 scanning lines. Here, how the one frame is displayed on the screen will be described with reference to the drawings.

FIG. 1 is a diagram showing the loci of scanning lines when one frame is formed by scanning two fields.

In the figure, first, the scanning of the first field is started from the point A at the upper left of the screen, and thereafter, the scanning is repeated on the solid line many times to reach the point B at the center of the lower end of the screen. At the point B, the display of the first field is completed, so the scanning line folds upward and rises to the upper edge of the screen, and the point C at the center of the upper edge.
Move to. Next, the second field scan starts from point C, and then folds back along the dotted line to point D at the lower right of the screen.
To reach. The scan line then returns to point A. One frame is completed by such interlaced scanning of two fields, that is, interlacing.

The period required for the scanning line to return from the point B to the point C or from the point D to the point A at each end of the field is called a vertical blanking period. This vertical blanking period is not a period for displaying an image on the screen but a period simply required for returning the scanning line to a predetermined position.Therefore, in order to prevent unnecessary images from being displayed on the screen during this period, Output is prohibited. This prohibition is actually due to a kind of masking processing for displaying black on the screen, and a processing process in which such masking processing and vertical synchronization are simultaneously performed is called vertical blanking.

The period of vertical blanking is determined by the configuration of the deflection circuit of the receiver, the size of the cathode ray tube, etc.
If this period is too long, the image quality is naturally affected. Therefore, for example, in the NTSC system, a numerical value of 21H (1H is a period corresponding to one scanning line) is set as the upper limit of the period. Here, vertical blanking in a conventional general television signal processing IC will be described.

FIG. 2 shows a portion related to vertical blanking in the internal circuit of the television signal processing IC, and I.
It is a block diagram showing an additional circuit required outside C.

In the figure, a television signal processing IC2
Has a vertical blanking pulse generator 4. The interior of the vertical blanking pulse generator 4 has a counter structure (not shown), and counts a period of 21H from the start of the vertical retrace line. That is, the counting of 21H is the vertical blanking period, and the pulse indicating this period is input as the vertical blanking pulse 6 to the vertical blanking processing unit 8 of the next stage.

An RY signal 10, a GY signal 12, and a BY signal 14 are input to the vertical blanking processing section 8. These three signals are ORed with the vertical blanking pulse 6 and output to the outside of the IC as an RY output signal 16, a GY output signal 18, and a BY output signal 20, respectively. These three output signals are converted into R signal 28, G signal 30 and B signal 32 by buffer transistors 22, 24 and 26, respectively, and a desired image is displayed on the cathode ray tube.

On the other hand, FIG. 3 is a signal waveform diagram showing the relationship between the vertical synchronizing pulse and the vertical blanking pulse 6.

As shown in the figure, the vertical sync pulse includes an equivalent pulse period EQ in 1 to 3H and 7 to 9H, and a vertical sync pulse period VSYNC in 4 to 6H, and is distinguished from a normal video signal by these pulse periods. .

Vertical blanking in the television signal processing IC 2 will be described with reference to FIGS. 2 and 3.

First, when the scanning of one field is completed, the vertical blanking period shown in FIG. 3 starts. Here, the vertical blanking pulse generator 4 continuously generates the vertical blanking pulse 6 for 21H so that an unnecessary image is not displayed on the screen. This signal is input to the vertical blanking processing unit 8, and the RY signal 10 and the GY signal 1 are input.
2. Mask the BY signal 14 to a high level. Therefore, black is displayed on the screen during this period.

On the other hand, when the period of 21H ends, the vertical blanking pulse 6 becomes low level, and the display of the video signal is restarted from 22H.

[0015]

As described above, in the vertical blanking period, image display is prohibited and scanning lines are retraced. However, the vertical blanking period differs depending on the television receiver, and depending on the design of the power supply circuit or the like, the blanking may not be completed within the period of 21H defined by the NTSC system. This problem is generally more pronounced in large receivers with large CRTs.

In such a case, in the worst case, the specification specified by the NTSC system is interrupted as the vertical blanking period, but the NTSC system does not specify that the video signal must be displayed immediately from 22H. In reality, each company deals with the following methods.

That is, for example, when the line between 22H and 24H is still in the retrace line, the vertical blanking period is extended by 3H outside the IC, and the display of the video signal during the retrace line is also prohibited. This is because the video signal after 22H is a signal transmitted as scanning is started from a predetermined position on the upper end of the screen, and it is known that if this is displayed during the retrace line, a very unnatural video will be displayed. This is because.

FIG. 4 is a diagram showing a circuit configuration for extending the vertical blanking period by an external circuit in the television signal processing IC of FIG. Here, the same reference numerals are given to the same configurations as those in FIG. 2, and the description thereof will be omitted. 5 is a signal waveform diagram showing vertical blanking by the circuit configuration of FIG.

In FIG. 4, a television signal processing IC
2 is added with an adjusting circuit 40 for further masking the RY output signal 16, the G-Y output signal 18, and the BY output signal 20 which are output from No. 2 and which are activated during the return line. The line period pulse 42 is input. This blanking period pulse 42 is given from a deflection circuit (not shown), which is possible because the deflection circuit recognizes the vertical blanking period. The blanking interval pulse 42 has the signal waveform shown in FIG.

The operation of the circuit configuration shown in FIG. 4 will be described.

According to this circuit configuration, during the period from 1H to 24H when the blanking period pulse 42 shown in FIG.
The signal 28, the G signal 30, and the B signal 32 are masked, and black is displayed on the screen. As a result, the vertical blanking period is extended by 3H, and it is possible to suppress the occurrence of unnatural bright lines.

In this case, the image actually displayed on the screen is the image after the extended vertical blanking period ends, that is, the image after 26H. In other words, 22H-2
Although the video corresponding to 4H will be cut,
This 3H is a number that can be ignored from the whole of one field, and the maximum H allowed for blanking extension depends on the design of each company.

The method for adjusting the vertical blanking period to cope with a television receiver having a long vertical blanking period has been described above. However, the conventional method causes the following problems.

[Problem 1] As is apparent from FIG. 5, during the period during which the blanking period pulse 42 is activated, the period during which the vertical blanking pulse 6 is masked in the television signal processing IC 2 is completely activated. Included in. Therefore, the vertical blanking pulse 6 becomes a completely meaningless signal, and the meaning of having such a mask processing function inside the television signal processing IC is lost.

[Problem 2] Since there is a blanking period pulse 42, it may be always used for the determination of the vertical blanking period, but in reality, such a design is not desirable. This is because this signal is supplied from a kind of power circuit called a deflection circuit, and problems such as malfunction due to superposition of noise and electromagnetic interference may occur. In general, when signals are transmitted from the circuit on the cathode ray tube side to the main substrate side, it is necessary to design the pattern of the substrate in consideration of the influence of noise and the like, which causes a burden on the design.

[Problem 3] On the other hand, television signal processing I
If it is considered that the vertical blanking period is set longer on the C side in advance, the versatility of the IC is lost. Generally, a larger television receiver needs to have a longer vertical blanking period, but a high-end device satisfies the NTSC system specifications as a result of giving due consideration to the deflection circuit design. This is because, for high-end models, satisfaction of such specifications has a part of the commercial value. Therefore, the IC design cannot be performed by uniformly extending the vertical blanking period.

[Problem 4] Similar to the problem 3, the vertical blanking period differs depending on the method other than NTSC, such as the PAL method. Therefore, when a television signal processing IC is used in a television receiver having various destinations, an IC having a vertical blanking period fixed at 21H cannot be dealt with as in the conventional case, and it is necessary to develop an IC for each method. Become.

[Purpose] The present invention has been made to solve the above-mentioned problems. The purpose of the present invention is to realize a specified vertical blanking period so that the vertical blanking period differs for each television receiver. It is an object of the present invention to provide an improved television signal processing IC capable of coping with the above.

[0029]

In order to solve the above-mentioned problems, a television signal processing IC of the present invention comprises a designation means for designating a vertical blanking period corresponding to a vertical blanking period of a television receiver. , Generating means for generating a desired vertical blanking period according to the designation by the designating means.

The television signal processing IC of the present invention
Includes a counter for outputting the count result to a plurality of count output pins by the specifying means including an input pin of the IC to which a voltage is applied, the generating means counting the number of horizontal synchronization signals, and the input pin. A selector for selecting a desired count value from the output of the count output pin according to the applied voltage, and a vertical blanking period is generated from the desired count value.

[0031]

According to the present invention having the above construction, the vertical blanking period can be designated according to the type of the receiver. Since the television signal processing IC generates the vertical blanking period according to this designation, the versatility of the IC is enhanced.

Further, according to the present invention, a desired count value of the horizontal synchronizing signal is selected according to the voltage applied from the input pin, and a vertical blanking period is generated from this count value.

[0033]

【Example】

Example 1. A preferred embodiment of the present invention will now be described with reference to the drawings.

FIG. 6 is a block diagram showing a portion related to vertical blanking in the internal circuit of the television signal processing IC 100 according to the embodiment of the present invention. Also in this figure, the same components as those in FIG.

A characteristic of this embodiment is that the television signal processing IC 100 has a designation input pin 102 for designating a vertical blanking period. A period designation signal 104 is input to the designation input pin 102, and designation by this signal is given to the improved vertical blanking pulse generation unit 106. Although the vertical blanking pulse generator 106 is composed of a counter as in the conventional case, it is different from the conventional example in that the numerical value to be counted can be selected from two ways.

FIG. 7 is a diagram showing the details of the vertical blanking pulse generator 106, which includes a counter 108 and a selector 110 for selecting a desired count value from its output. The period specifying signal 104 is given to the selector 110. Here, the counter 108 is an existing counter required to detect the start point of a frame or field, and this is used in this embodiment. Therefore, a clock having a frequency twice that of the horizontal synchronizing signal is input to the counter 108 in order to detect a field with a fraction of 0.5H. Further, a vertical synchronizing signal is input to the reset terminal in order to reset the counter 108 for each field.

In this embodiment, the vertical blanking pulse generator 1 is responsive to the voltage applied to the designated input pin 102.
06 selects the vertical blanking period from two periods of 21H or 24H. More specifically,
If the voltage applied to the designated input pin 102 is high level, 21H, and if it is low level, the vertical blanking pulse 6 of 24H is output.

The operation of this embodiment will now be described with reference to this drawing.

Now, suppose that this television signal processing IC1 is
Consider that 00 is built into a large-sized television receiver. This receiver has a long blanking period as described with reference to FIG. 5, and requires a vertical blanking period of 1 to 24H.

In this case, the television signal processing IC 10
When designing a circuit board (not shown) on which 0 is mounted, the designated input pin 102 may be grounded to a low level.
As a result, the vertical blanking period is extended to 24H, and desired blanking can be performed. The vertical blanking pulse at this time corresponds to 42 in FIG.

On the other hand, a receiver which does not require such extension,
That is, in a receiver that satisfies the NTSC system specifications, the designated input pin 102 may be fixed to a high level on the circuit board. In this case, the vertical blanking period is 21
It becomes H, and it becomes possible to perform the desired blanking. The vertical blanking pulse at this time is 6 in FIG.
Matches

As described above, according to this embodiment, since the vertical blanking period can be adjusted, it is not necessary to provide an additional circuit outside the television signal processing IC as in the conventional case.

The following various modifications can be made to this embodiment.

1. The designated input pin 102 is pulled up inside the television signal processing IC 100. In this case, if the receiver does not need to extend the vertical blanking period, there is an advantage that the designated input pin 102 can be used in a non-connected state.

2. The designated input pin 102 is also used as a pin for inputting an AC signal. Only the voltage level matters as the designated input, while only the change in the voltage is referred to inside the IC when the AC signal is input. Therefore, it is possible to share the signal pin by extracting the DC component and the AC component from this pin, respectively. As a result, it is not necessary to increase the number of IC pins.

3. When the television signal processing IC operates by receiving an instruction from an element such as a microcomputer, the vertical blanking period can be designated by the microcomputer. In this case, since the designated value can be stored in its own I / O register or the like, it becomes possible to further designate various vertical blanking periods.

4. When the television signal processing IC itself has a programmable memory area, the vertical blanking period may be stored in this memory according to the receiver. Also in this case, a versatile television signal processing IC
Can be realized.

Example 2. In the first embodiment, the vertical blanking pulse is binary-selected according to the voltage applied to the designated input pin 102. In this embodiment, more selections are possible. Only the differences from the first embodiment will be described below with reference to FIG. FIG. 8 is a diagram illustrating details of the vertical blanking pulse generation unit 106 according to the second embodiment.

1. Regarding the counter 108 In the second embodiment, 21H and 24H from the counter 108 described above.
Not only that, 22H and 23H should also be pulled out.

2. Designated input pin 102 By dividing the DC voltage applied to this pin into four sections, one count value is designated from 21 to 24H.

3. A plurality of window comparators are prepared for the selector 110, and it is determined which of the four divisions the voltage applied to the designated input pin 102 belongs to. A desired count value is selected according to the determination result.

The outline of the second embodiment has been described above, but it is more effective to extract a larger count value from the counter 108.

[0053]

As described above in detail, according to the television signal processing IC of the present invention, the vertical blanking period can be designated, so that the vertical blanking period according to the receiver can be realized. it can. At this time, it is possible to easily specify by applying different voltages to the input pins. As a result, although it is one television signal processing IC, it is possible to deal with various receivers and destinations, and the versatility of the IC can be improved.

Further, according to the present invention, since the vertical blanking period can be adjusted inside the IC, it is not necessary to provide an additional circuit outside the IC as in the conventional case. Further, since the blanking period pulse required in the conventional additional circuit is unnecessary, it is not necessary to receive such pulse from the power circuit such as the deflection circuit, and malfunctions due to noise, electromagnetic interference, difficulty in board design, etc. The problem can be completely resolved.

[Brief description of drawings]

FIG. 1 is a diagram showing a locus of scanning lines when one frame is formed by scanning two fields.

FIG. 2 is a circuit diagram showing an internal circuit of a television signal processing IC.
FIG. 6 is a configuration diagram showing a portion related to vertical blanking and an additional circuit required outside the IC.

FIG. 3 Vertical blanking and vertical blanking pulse 6
It is a signal waveform diagram showing the relationship of.

4 is a diagram showing a circuit configuration in the television signal processing IC of FIG. 2 in which a vertical blanking period is extended by an external circuit.

5 is a signal waveform diagram showing vertical blanking by the circuit configuration of FIG.

FIG. 6 is a television signal processing I according to the embodiment of the present invention.
It is a block diagram which showed the part relevant to vertical blanking among the internal circuits of C100.

FIG. 7 is a diagram showing details of the vertical blanking pulse generator 106 according to the first embodiment.

FIG. 8 is a diagram illustrating details of a vertical blanking pulse generator 106 according to the second embodiment.

[Explanation of symbols]

 8 Vertical Blanking Processing Unit 10 RY Signal 12 GY Signal 14 BY Signal 16 RY Output Signal 18 GY Output Signal 20 BY Output Signal 100 Television Signal Processing IC 102 Designated Input Pin 106 Vertical blanking pulse generator 108 Counter 110 Selector

Claims (2)

[Claims] 1. An IC for generating a video signal from a television signal received by a television receiver, and designating means for designating a vertical blanking period corresponding to a vertical blanking period of the television receiver. And a generation means for generating a desired vertical blanking period according to the designation by the designation means. 2. The television signal processing IC according to claim 1, wherein the designation means includes an input pin of the IC to which a voltage is applied, and the generation means counts the number of horizontal synchronization signals, A counter that outputs a count result to a plurality of count output pins; and a selector that selects a desired count value from the output of the count output pin according to a voltage applied from the input pin, A television signal processing IC characterized in that a blanking period is generated.