JPH0760306B2 - Screen display - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen display device capable of preventing a display position of a character / graphic displayed on a screen from being mistaken.

2. Description of the Related Art Conventionally, many screen display devices have been used which display characters / graphics on a screen and display various information in an easy-to-understand manner.

The conventional screen display device will be described below. FIG. 1 is a block diagram of a conventional screen display device. 1 is an oscillator, a presettable counter (hereinafter abbreviated as P counter)
2 is connected to the clock input and the input of the gate 4, the output of the P counter 2 is connected to the input of the RS flip-flop (hereinafter abbreviated as RSFF) 3, and the horizontal synchronizing pulse is the reset input of the P counter 2 and the reset of RSFF3. It is connected to the input and the clock input of the P counter 6 and the input of the gate 8. The output of RSFF3 is connected to the input of gate 4, the output of gate 4 is connected to the input of counter 5, and counter 5
The output of is connected to the input of the data memory 12. The vertical synchronizing pulse is connected to the reset input of the P counter 6 and the reset input of RSFF7, and the output of the P counter 6 is RSFF7.
, The output of RSFF7 is connected to the input of gate 8, the output of gate 8 is connected to the clock input of counter 9, the output of counter 9 is connected to data memory 12, and the output of data memory 12 is Display output. The output of the latch A10 is connected to the P counter 2, the output of the latch B11 is connected to the P counter 6, and the data memory 12, the latch A10 and the latch B11 are connected to the data line.

The operation of the screen display device configured as described above will be described below.

First, horizontal position data is set in the latch A10. This set value is set in the P counter 2 at the timing of the horizontal synchronizing pulse, and the gate 4 is closed while the output of the oscillator 1 is counted up to this set value. After that, the gate 4 is opened and the output of the oscillator 1 is input to the counter 5. That is, since the output of the oscillator 1 is not applied to the counter 5 up to the value set by the latch A10, the read signal of the horizontal position is not output during that time. When the read signal in the horizontal direction is not applied to the memory, the period up to that point on the horizontal scanning line is set as the period not displayed, and when the output of the oscillator 1 is counted by the P counter 2 to the value set by the latch A10. A horizontal read signal is applied to the memory, and a displayable period starts from this point, and the dot position on the horizontal scanning line at this time is set as the horizontal display position. Similarly for the vertical direction,
Vertical position data is set in the latch B11. This set value is set in the P counter 6 at the timing of the vertical synchronizing pulse, and while the horizontal synchronizing pulse is counted up to this setting,
Gate 8 is closed. After that, the gate 8 is opened and the horizontal synchronizing pulse is input to the counter 9. That is, latch B11
Since the horizontal synchronizing pulse is not applied to the counter 9 up to the value set in, the vertical position read signal is not output during that time, so the vertical read signal for reading the display data from the memory is applied to the memory. However, when the horizontal synchronizing pulse is counted up to the value set in the latch B11 in the P counter 6, the vertical reading signal is applied to the memory. Display is possible from the horizontal scanning line at this time, and the position of the horizontal scanning line at this time is set as the display position of the vertical method. The point set as the horizontal display position on the horizontal scanning line becomes the display position on the screen, and the display data is output from the memory.

However, in the above configuration, the horizontal position setting and the vertical position setting are independent, and the horizontal position setting is performed for each horizontal synchronizing pulse, and the setting cycle is 64 μs of one horizontal period.
While the setting can be updated more than 260 times within the field period, the vertical position is set for each vertical sync pulse, so the setting is updated once per field period. Will be updated sooner. for that reason,
When displaying various characters at different positions one after another, such as when displaying characters, the horizontal display position is 1
While the setting is updated one after another within the field period, the vertical position setting is not updated during the field period and remains at the display position as it is, and the display appears at another position on the screen. Had the problem.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide a screen display device in which display at a wrong position in the screen display is prevented.

Configuration of the Invention The present invention is a screen display device for determining the display position on the screen based on the horizontal sync pulse and the vertical sync pulse,
By providing the means for simultaneously setting the horizontal position and the vertical position, it is possible to prevent the display at the wrong position.

Description of Embodiments FIG. 2 is a block diagram of a screen display device according to an embodiment of the present invention.

22 is a latch A1 whose output is connected to the P counter 14 and whose latch pulse is connected to the vertical synchronizing pulse. 23 is a latch A2, the output of which is connected to the latch A1 of 22 and the input of which is connected to the data line. In addition, 13 is an oscillator, 14 is a presettable counter, 15 is an RS flip-flop, 16
Is a gate, 17 is a counter, 18 is a presettable counter, 19 is an RS flip-flop, 20 is a gate, 21 is a counter, 24 is a latch, and 25 is a data memory, which have the same configurations as those of the conventional example.

The operation of the screen display device of this embodiment configured as described above will be described below. First, the horizontal position data is held in the latch A2 of 23.
Is connected to the presettable counter 14 through the latch A1. Further, the latch input of the latch A1 of 22 is a vertical synchronizing pulse, and no matter what timing the horizontal position data is set to the latch A2 of 23, new data is set in the P counter 14 by the vertical synchronizing pulse. It will be later. The other operations are the same as in the conventional example.

As described above, according to the configuration of the present embodiment, it is possible to set the horizontal position and the vertical position at the same time, it is possible to prevent the display at the wrong position, the change from the conventional example is easy, and the performance is inexpensive. Can be improved.

In this embodiment, the latch is added to synchronize with the vertical synchronizing pulse, but the same effect can be obtained even if the horizontal position is set during the vertical synchronizing period without adding the latch. In this case, an additional circuit called a latch is unnecessary, but there is a time constraint that the vertical synchronization period must be detected and data must be set during that period.

As described above, the present invention is provided with the means for simultaneously setting the horizontal position setting and the vertical position setting. Therefore, since the horizontal position and the vertical position are at the same positions as set,
The display position on the screen can be displayed without shifting from the set position.

[Brief description of drawings]

FIG. 1 is a block diagram of a conventional screen display device, and FIG. 2 is a block diagram of a screen display device according to an embodiment of the present invention. 1,13 …… Oscillator, 2,6,14,18 …… Presettable counter, 3,7,15,19 …… RS flip-flop, 4,8,16,20 ……
Gate, 5,9,17,21 …… Counter, 10,11,22,23,24 ……
Latch, 12,25 ... Data memory.

Claims (1)

[Claims] 1. A horizontal and vertical position on a screen is determined on the basis of a horizontal sync pulse and a vertical sync pulse in order to display a character / graphic corresponding to digital data by superimposing it on a display screen displayed on the screen. A screen display device, wherein the horizontal position data output from the horizontal position data holding means is set at the timing of horizontal synchronization, and a first presettable counter for counting the output of the oscillator to this set value, and vertical position data holding The vertical position data output from the means is set at the timing of vertical synchronization, and a second presettable counter for counting horizontal synchronization pulses up to this set value, and the first presettable counter for the oscillator up to the set value. After counting the output, input the output of the oscillator to the horizontal position read counter and The first gate means for resetting the input of the oscillator output to the horizontal position read counter by every one horizontal scanning period, and the second presettable counter horizontally after counting the horizontal synchronizing pulse to the set value. Second gate means for inputting a sync pulse to the vertical position read counter and resetting the input of the horizontal sync pulse to the vertical position read counter by the vertical sync pulse every vertical scanning period; and the horizontal position data holding means. And horizontal / vertical position setting synchronizing means for outputting both the data from the vertical position data holding means in synchronization with the vertical synchronizing pulse period,
According to the horizontal position and vertical position data set at the same time by the horizontal / vertical position setting synchronizing means, the horizontal position reading counter and the vertical position reading counter
A screen display device characterized in that display data is read out from a memory in which characters and figures are stored and a display signal is output.