JPH0779475B2 - Character multiplex broadcasting receiver - Google Patents

Description

TECHNICAL FIELD The present invention relates to a television character multiplex broadcasting receiver, and more particularly to a display output circuit thereof.

(Prior Art) In recent years, a character multiplex broadcasting service has been performed in which image information including characters and figures is transmitted in the form of a digital signal while being superimposed on a vertical blanking period of a television wave. Regarding the coloring of characters, there are two types of coloring, one for each functional block, that is, a foreground color and a background color, and another for each logical pixel. Is distinguished from Level A. In the function of level A, the types of coloring are basically 8 colors with maximum brightness, 7 colors with reduced brightness, and 16 colors with transparency.

In the level A teletext receiver, the character signal superimposed on the vertical blanking period of the television wave is extracted, the data is decoded, stored in the display memory, and synchronized from the display memory to the synchronization signal to be displayed. Then, the brightness information, the foreground color, the background color, and the attribute information are combined, and the total brightness and the brightness are lowered for each pixel (hereinafter referred to as half-brightness). Take the way to display.

The display control unit is generally integrated into a circuit in terms of productivity and cost.

FIG. 2 shows an example of a display output circuit of a conventional teletext receiver. In the figure, B indicates an output part of the integrated display control part, and red (R), green (G), blue (B) and a signal (Z) indicating half luminance are output buffers 21, 22, respectively. 2
It is output to the output pins R, G, B, Z via 3,24. Pin R,
The outputs r, g, b, z of G, B, Z are binary and take the level values of the power supply V _CC and the ground V _SS . 2-input AND gate 25,26,27,28,29,30
Is an open collector output and has 2 inputs and gate 25
The input terminal of r is connected to r and the power supply V _CC , and the output terminal is connected to the resistor 31. The input terminal of the AND gate 26 is connected to r and z, and the output terminal is connected to the resistor 32. The other ends of the resistors 31 and 32 are connected to the base of the transistor 33. Transistor
One end of resistors 34 and 35 is connected to the base of 33, and resistor 3
The other end of 4 is connected to the collector of transistor 33,
Connected to _CC . The other end of the resistor 35 is connected to the ground. The emitter of the transistor 33 is connected to the ground via the resistor 36. The transistor 33 serves as an emitter follower, and its emitter output is output as the output signal R ₀ via the resistor 37 and the capacitor 38. The other outputs G ₀ and B ₀ have the same structure, except that g is input to one of the two-input AND gates 27 and 28 and b is input to one of the two-input AND gates 29 and 30.

Next, the operation will be described by taking as an example the case where full-brightness red and half-brightness red are output, and the case where red is not output.

In the case of full-brightness red, r and z are at a high level, and the voltage divided by the resistors 34 and 35 is applied to the base of the transistor 33. In the case of half-bright red, r is at a high level, z is at a low level, and a voltage divided by the parallel resistance values of the resistor 34, the resistor 35, and the resistor 32 is applied to the base of the transistor 33. When red is not output, both r and z are low level,
The base voltage of the transistor 33 is the resistor 34 and the resistors 31, 32,
The voltage is divided by 35 parallel values. Therefore, if the values of the resistors 31, 32, 34 and ₃₅ are selected, a three-valued output can be obtained as R ₀ . The remaining G ₀ and B ₀ have the same operation, and these R
It is possible to display 16 colors with a combination of three values of ₀ , G ₀ and B ₀ .

(Problems to be Solved by the Invention) The above method requires an output pin for half-brightness control. If a D / A conversion circuit is provided inside to reduce the number of pins, an analog circuit will be provided inside the IC circuit, and there is a drawback that the cost will increase due to inspection of the IC.

The object of the present invention is to solve the conventional drawbacks and to output 16-color output of character multiplex broadcasting level A without outputting an output pin for half-brightness control and without having a D / A conversion circuit inside the IC. It is to provide a display output circuit that can perform.

(Means for Solving Problems) In the present invention, signal outputs indicating red, green, and blue are output via a tri-state output buffer, and each tri-state output buffer has luminance information of full luminance and half luminance. , And a signal indicating each color to obtain a three-level output of high level, low level, and open, and an integrated display control unit, and a resistor and a transistor connected to the output to control three It is provided with a display output circuit including a voltage conversion unit that performs 16-color display by converting the voltage level.

(Operation) According to the above configuration, it is possible to reduce the number of pins for display output, and it is possible to perform 16-color display without increasing the cost required for inspection without having a D / A in the IC. .

(Example) An example of the present invention will be described with reference to FIG. FIG. 1 shows a display output circuit of a character multiplex broadcasting receiver of the present invention. In the figure, the block A is integrated. 1,2,3 are tri-state output buffers, 4,5,6 are 2
The input AND gate 7 is an inverter, which constitutes a display control unit. (R), (G),
(B) and (Z) are signals indicating red, green, blue, and luminance information, respectively. (R) is connected to the input of the tri-state output buffer 1, and the output is output from the pin R. (G) and (B) are connected to the tri-state output buffers 2 and 3. An inverted signal of a signal (R) indicating red and a signal (Z) indicating luminance information is input to the 2-input AND gate 4, and the tristate control end of the output tristate output buffer 1 is connected to the 2-input AND gate 4. Similarly 2
Input AND gates 5 and 6 are supplied with signals indicating green (G) and blue (B) and an inverted signal of a signal (Z) indicating luminance information, and outputs are tristate output of tristate output buffers 2 and 3. It is connected to the control end. A signal (Z) indicating brightness information is input to the inverter 7.

The resistor 8 is connected to the pin R, and the other end thereof is connected to the base of the transistor 9. The resistor 10 has one end connected to the base of the transistor 9 and the other end connected to the power supply V _CC . The resistor 11 has one end connected to the base of the transistor 9 and the other end connected to the ground. The collector of the transistor 9 is connected to the power supply V _CC , and the emitter is connected to the ground via the resistor 12. The signal R ₀ is output from the emitter of the transistor 9 via the resistor 13 and the capacitor 14. The other outputs G ₀ and B ₀ have the same configuration, and the inputs to the tri-state output buffers 2 and 3 and the input signals to the 2-input AND gates 5 and 6 are (G) and (B). The difference is that Incidentally, resistors 8, 10, 11, 12, 13, ..., Transistor 9,
The capacitor and the capacitors 14 constitute a voltage converter.

The operation of the display output circuit configured as above will be described. When showing all brightness red, (R) is a high level, (Z) is a high level, and (G) and (B) are a low level. Therefore, the output of the inverter 7 is at the low level, the tri-state output buffer 1 is in the output mode, and the signal r at the high level is output from the pin R. As a result, the base voltage of the transistor 9 becomes a voltage divided by the parallel resistance value of the resistor 8 and the resistor 10 and the resistor 11. When red is not output, (R) is at low level, the tri-state output buffer 1 output mode is set regardless of the value of (Z), and the pin R is at low level (ground). Therefore, the base voltage of the transistor 9 becomes a voltage value divided by the parallel resistance value of the resistor 10, the resistor 8, and the resistor 11. In the case of half-bright red, (R) is high level and (Z) is low level, so 2
The output of the input AND gate 4 becomes high level, the tristate output buffer 1 becomes tristate,
The base voltage of the transistor 9 has a value divided by the resistor 10 and the resistor 11. Therefore, if the resistance values of the resistors 8, 10 and 11 are selected, three values of full-brightness red, half-brightness red, and no red output are output as R ₀ . Other circuits also operate in the same manner and can display 16 colors by combining these R ₀ , G ₀ , and B ₀ .

(Effects of the Invention) According to the present invention, red, green, and blue outputs are output via the tri-state output buffer, and each tri-state output buffer is provided with a signal indicating luminance information (full luminance, half luminance), By controlling with the signal of each color, the output pin is red, green,
It is possible to perform 16-color display with three blue lines, and it is possible to provide a display output section of a display control section which is less expensive than the conventional method.

[Brief description of drawings]

FIG. 1 is a display output circuit diagram of a character multiplex broadcasting receiver according to an embodiment of the present invention, and FIG. 2 is a conventional display control output circuit diagram. 1,2,3 …… Tri-state output buffer, 4,5,6 …… Input and gate, 7 …… Inverter, 8,10,11,12,13 ……
Resistor, 9 ... Transistor, 14 ... Capacitor.

Claims (1)

[Claims] 1. A signal output indicating red, green, and blue is output via a tri-state output buffer, and each tri-state output buffer indicates a signal indicating luminance information of full luminance and half luminance and each color. By controlling with a signal, an integrated display control unit for obtaining a three-level output of high level, low level and open, and by converting into three voltage levels by a resistor and a transistor connected to the output 16 A character multiplex broadcast receiving apparatus comprising a display output circuit including a voltage conversion unit for performing color display.