JPH0425889A - Image display circuit - Google Patents

Abstract

PURPOSE:To display an image without adding an output function to the image display circuit by providing a function for outputting a signal other than an image display signal in a vertical synchronizing period to an output terminal which outputs the image display signal. CONSTITUTION:When an image display system control output signal 8 which is outputted by a microcomputer 2 during the vertical synchronizing period is inputted to a NAND circuit 4, the control output signal of an image display system which has the opposite polarity from the input is outputted to the output terminal of the circuit 4. At this time, an image display signal generating circuit 3 does not output a negative image signal 9, so the control output signal of the image display system which is outputted by the microcomputer 2 is outputted to the output, i.e. image output terminal of a NAND circuit 5. A negative image signal 9 which is outputted by the generating circuit 3 is inputted to the NAND circuit 5 except during the vertical synchronizing period and horizontal synchronizing period and the signal having the opposite polarity from the negative image signal is outputted to the image output terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a control function of a system for displaying images.

2. Description of the Related Art A conventional image display circuit is shown in FIG. In Figure 3,
1 is an image display circuit, 2 is an image display signal generation circuit, 3 is a horizontal synchronization signal, 4 is a vertical synchronization signal, and 5 is an image output signal. A conventional image display circuit converts an image signal 5 outputted from an image display signal generation circuit 2 into a vertical synchronization signal 4 for image display. The image signal is output from the image signal output terminal 6 in synchronization with the horizontal synchronizing signal 3.

Problem to be Solved by the Invention When all the output terminals of an image display circuit are completely assigned to control the system that performs display, when the need for further control of the image display system arises, it must be dealt with by adding more output terminals. However, there are also issues such as increased costs and design man-hours.

Means for Solving the Problems The present invention solves the problems described above by providing an output terminal for outputting an image display signal with a function of outputting a signal other than the image display signal during the vertical synchronization period.

According to the present invention, the output terminal that outputs the image display signal has a function of outputting a signal other than the image display signal during the vertical synchronization period, so that image display can be performed without adding an output function to the image display circuit. You can get the means to control the system.

EXAMPLE Below, an image display circuit using a microcomputer as a mechanism having a control function of a system for displaying images, which is an example of the present invention, will be described with reference to the drawings.

FIG. 1 is a block diagram of an image display circuit. FIG. 2 shows a time chart. In FIG. 1, 1 is an image display circuit, 2 is a microcombiner, 3 is an image display signal generation circuit, 4 is a first NAND circuit, and 5 is a second NA
ND circuit, 6 is a horizontal synchronization signal, 7 is a vertical synchronization signal, 8 is a control output signal of the image display system, 9 is a Tu image m number (however, in this case, it is an inverted image signal, and hereinafter, it will be referred to as a negative image signal) ), 10 is an image output signal, and 11 is an image output terminal.

When the control output signal 8 of the image display system output from the microcomputer 2 during the vertical synchronization period is input to the first NAND circuit 4, the output terminal of the first NAND circuit 4 receives an image having the opposite polarity to the input. A control output signal of the display system is output. On the other hand, during the vertical synchronization period and the horizontal synchronization period, the image display signal generation circuit 3 does not output the negative image signal 9, so an "H" level signal is input to the second NAND circuit. Therefore, the second N
A control output signal of the image display system outputted from the microcomputer 2 is outputted to the output of the AND circuit, that is, the image output terminal.

Outside the vertical synchronization period and outside the horizontal synchronization period, the first NAN
Since the "L" level vertical synchronizing signal is input to the D circuit, the first NAND circuit always outputs an "H" level signal, which is input to the second NAND circuit. On the other hand, the negative image signal 9 output from the image display signal generation circuit 3 is input to the second NAND circuit 5, and a signal having the opposite polarity to the negative image signal is output to the image output terminal.

FIG. 2 shows the time chart. (at is the vertical synchronization signal, (bl is the horizontal synchronization signal, fc) is the image signal, (
d) is the control output signal of the image display system, te
l is an image output signal.

During the vertical synchronization period, +a+ is the control output signal ID of the image display system output from the microcomputer 2.
) is the output signal tel of the image output terminal, outside the vertical synchronization period (al) and outside the horizontal synchronization period (bl is the negative image signal (C) output from the image display signal generation circuit 3 is the output signal of the image output terminal. fe).

Effects of the Invention According to the present invention, by having the function of outputting a signal other than the image display signal during the vertical synchronization period to the output terminal that outputs the image display signal, it is possible to control a system in which all the output terminals of the image display circuit perform display. Furthermore, even if it becomes necessary to control the image display system, it is possible to control the image display system without adding additional output terminals.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram of an image display circuit according to an embodiment of the present invention, FIG. 2 is a time chart 1, and FIG. 3 is a conventional image display circuit. 1... Image display circuit, 2... Microcomputer, 3... Image display signal generation circuit,
4.5...NAND circuit. No. 6, 5 Mi, 15 Gozusumi, 5 Anba-2, Micro Combiator 3, Image Izogoten, Sugi issue origination circuit 4, 7th NAND m foot each 5, 2 (7) NANO [] IA4 No. 7 placed flat on Fushimi 6 and 7, tIlrEl18a No. ε・-I east bag, screw stem control sword No. 43 No. 9
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Claims (1)

[Claims] An image display circuit characterized in that it has a function of outputting a signal other than the image display signal during a vertical synchronization period to an output terminal that outputs the image display signal.