JPH0157368B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is an image display device that displays a pattern according to data written in a digital memory. The present invention relates to a video display device in which data (color display information, etc.) to be displayed at an opposing position, that is, a designated position, can be written to an address in a digital memory allocated to correspond to the designated position.

By moving the light pen's indicated position, the above-mentioned video display device writes color display information one after another to the address of the digital memory according to the movement trajectory, and the display according to the written contents is displayed on the CRT.
Since it is carried out on a regular basis, it can be called a television blackboard system in which the CRT is used as a blackboard and the light pen is used as a pencil.

By the way, in such a device, old data is erased as new data is written, so for example, when coloring after drawing an outline, the outline may be erased, making it difficult to complete the image. It often causes inconvenience. The present invention has been made with the aim of eliminating such inconveniences, and has a structure in which, for data that is not desired to be erased, the write signal for the address where the data is written is disabled. To provide a video display device which prohibits rewriting and prevents already drawn patterns from being inadvertently erased. The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 is a block diagram schematically showing the main parts of a video display device according to the present invention, and FIGS. 2A to 2A are timing charts for explaining the operation. In the figure, 1 is a control circuit that outputs various timing signals, etc.; 4
numeral 6 denotes a digital memory into which data to be displayed is written; numeral 6 denotes a CRT serving as an image display section; and numeral 7 denotes a light pen for indicating the writing position.

The light pen 7 emits a signal LPN that reports the indicated position on the screen of the CRT 6. This signal is emitted when the light receiving section of the light pen 7 captures the light of the raster line passing through the indicated position. It is input to the decision holding circuit 8. The control circuit 1 generates a pulsed write signal as shown in FIG. 2 N during the non-display period (the period in which the display period signal E shown in FIG. 2 C and G is at a low level) immediately after this signal is applied. It is set so that only one C is fired.

The indicated position signal LPN is shown in FIG.
As shown in an enlarged view in FIG. 2, the clock φ generated by the control circuit 1 (see FIG. The selection circuit 3 determines and holds the address Pxy of the digital memory 4 corresponding to the indicated position on the CRT, and uses this as the write address.
It is configured to output to.

The control circuit 1 receives a vertical synchronizing signal V [Fig. 2 A] necessary for display on the CRT 6, and a horizontal synchronizing signal H as well.
[Fig. 2 E] The display period signal E is at a high level during a period excluding appropriate time periods before and after the pulse of the horizontal synchronizing signal H, and while the display period signal E is at a high level.
The above-mentioned clock φ and the write signal C, which appear at a rate of one pulse per pixel on the CRT screen, are output.

The clock φ is not only applied to the address determination holding circuit 8 as described above, but also applied to the counter 2 for creating a read address. The counter 2 updates the read address Qxy according to the input of the clock φ, and inputs this to the selection circuit 3. While the display period signal E is at a high level, the selection circuit 3 uses the read address Qxy as its output Rxy, and also outputs the signal E.
While Pxy is at low level, the write address Pxy is selected as its output Rxy and this is stored in digital memory 4.
It is meant to be given to. And the write signal C is
It is provided as one input of the AND gate 11.

The digital memory 4 includes an address signal Rxy which is the output of the selection circuit 3 mentioned above, a write enable signal WE which is the output of the AND gate 11 and which allows data writing when it is at a high level, and circuits such as registers (not shown). Write data B given from
is input and the write enable signal WE is at high level, the digital memory 4
enters write mode and writes write signal data B to the address specified by address signal Rxy. Conversely, when the write enable signal WE is at a low level, the digital memory 4 enters the read mode and reads data at the address specified by the address signal Rxy.

The data read from digital memory 4 is
D/A (digital/
While the signal is input to the analog) conversion circuit 5, it is also input to the matching circuit 9. Rewriting prohibited data (i.e., data that is not desired to be erased) A set in a register or the like is also input to this matching circuit 9.
The matching circuit 9 compares both input data, and when the two match, it issues a high level matching signal, and this signal is passed through the inverter 10 to the AND gate 1.
1 so that it can be applied to the other input terminal. Since the inverter 10 inverts the input signal and outputs it, the inverter 10 outputs the mismatch signal D (the mismatch signal D), which goes low level when both input data match and goes high when they don't match. 2) will be issued.

The apparatus of the present invention constructed as described above operates as follows. First, looking at the display, the read address Qxy obtained by the counter 2 is selected by the selection circuit 3 while the display period signal E is at a high level, and the content specified by the selected address signal Rxy is It is read out sequentially, and the read content is converted into an analog signal by the D/A conversion circuit 5 and sent to the CRT 5.
Display is performed according to the read data. Note that during such display, the write signal C remains at a low level, so the write enable signal WE never becomes a high level.

Now, if you want to draw a horizontally long rectangle in green, for example, on the CRT 6 as shown in FIG. Accordingly
Move it on CRT6. Then, as the light pen 7 moves, the indicated position signal LPN will change, and the write address Pxy will also change accordingly, but at this write address Pxy, the display period signal E is at a low level. During the non-display period of the CRT, the selection circuit 3 selects the address signal Rxy and applies it to the digital memory 4, and the write signal C is issued once per field, and furthermore, at this time, rewriting is prohibited. Since the data A is not set, the mismatch signal D is always at a high level, and the write enable signal WE, which is the same as the write signal C, is eventually given to the digital memory 4. Data for green display is written to the address of Rxy = Pxy, which changes sequentially as it moves. The written data will be displayed on the CRT from the next display period.
FIG. 2H shows the state of change when the signal F applied to the green display displays a rectangular shape as shown in FIG.

Now, if you change the contents of write data B (for example, change it to data corresponding to red) and perform a drawing operation with the light pen 7, that is, if you change the content of the write data B to the data corresponding to the color red, and then perform a drawing operation with the light pen 7,
When you move it on the screen, the red color will be displayed accordingly, but if you do not want the green display part to be erased by the red display, for example, you can move the red color inside the green rectangle. If you want to color it, set data associated with green as the rewrite prohibited data A. When the rewrite prohibition data A is set in this way, when the approximate center of the upper side of the green rectangle is pointed with a light pen as shown in FIG. 3, the pointed position signal LPN is as shown in FIG.
As is clear from the comparison of 2 and 3, while signal F is at high level, that is, read address Qxy is selected and Rxy
is applied to the digital memory 4, and the indicated position signal LPN is obtained while reading out the data related to the green display stored at that address. In the non-display period immediately after the display period in which this signal LPN is obtained, the write signal C becomes high level. However, during this non-display period, the address signal Rxy given from the selection circuit 3 to the digital memory 4 is the designated position signal obtained from the light pen 7 that designated the green display position.
This is the address Pxy determined by the LPN, and the contents of this address Pxy correspond to the color green. During the non-display period, the write enable signal WE is at a low level until C becomes a high level, so the contents of this address Pxy are read out and input to the matching circuit 9, but in this case, rewriting is prohibited. Since the data A and the contents of address Pxy match, the mismatch signal D becomes low level, and even if the write signal C becomes high level, the write enable signal WE remains low level, and the write to address Pxy is written to the above address Pxy. Writing data B, that is, changing the display from green to red, is not performed. This also applies when pointing to other green display areas with a light pen. Of course, you can freely rewrite and write to the display portions of other colors. When data other than the data corresponding to the green display is set as the rewrite prohibited data A, or when no setting is made and the green display section is pointed with a light pen, the mismatch signal D becomes high level and the write signal is When C goes high, the write enable signal WE goes high as shown by the two-dot chain line in Figure 2, and write data B is written to the address Pxy determined at the indicated position. Become.

As described above, the video display device of the present invention displays an image by data including a plurality of display color information, apart from the background color, which is stored in a memory that associates a position on the video display section with its address. is displayed on the video display section, and data is written to the memory address corresponding to the position on the video display section indicated by the light pen, so that a drawn image corresponding to the movement locus of the position indicated by the light pen is displayed on the video display section. In a video display device that displays , the contents of the memory address corresponding to the position on the video display section indicated by the light pen are read during the non-display period of the video display section, and this read content and a preset A writing signal is generated during the non-display period of the video display section based on a means for comparing the rewrite prohibited data including display color and a signal obtained when a position on the video display section is indicated with a light pen. and means for validating the write signal to permit data writing to the memory if the comparison results between the read content and the rewrite prohibited data do not match, and disabling the write signal if they match. This makes it easier to operate the light pen when displaying a pattern image, such as coloring other parts while leaving the outline, etc., and has the effect of significantly improving the operability of this type of device. can get.

[Brief explanation of drawings]

FIG. 1 is a block diagram schematically showing the main parts of the device of the present invention, FIGS. 2A to 2 are timing charts for explaining the operation, and FIG.
FIG. 3 is a front view of a CRT. DESCRIPTION OF SYMBOLS 1... Control circuit, 2... Counter, 3... Selection circuit, 4... Digital memory, 5... D/A conversion circuit, 6... CRT, 7... Light pen, 8...
... Address determination holding circuit, 9 ... Matching circuit, 10
...Inverter, 11...AND gate.

Claims (1)

[Claims] 1. Displaying a selected image on a video display section using data containing a plurality of pieces of display color information, apart from the background color, stored in a memory that associates positions on the video display section with their addresses. A video image that displays a drawn image corresponding to the movement locus of the position indicated by the light pen on the video display section by displaying data on the memory address corresponding to the position on the video display section indicated by the light pen. In the display device, the content of the address in the memory corresponding to the position on the video display section indicated by the light pen is read out during the non-display period of the video display section, and this read content is combined with the preset display color. and a means for emitting a write signal during a non-display period of the video display section based on a signal obtained when a position on the video display section is indicated with a light pen. means for validating the write signal to permit data writing to the memory if the comparison result between the read content and the rewrite prohibited data does not match, and disabling the write signal if they match; A video display device characterized by: