JPH08339285A - Screen scroll controller - Google Patents

Abstract

PURPOSE: To scroll a screen at a high speed without using a special memory. CONSTITUTION: In this screen scroll controller, a display ASIC9 is connected between a plotting memory 4 and a display memory 5. When scrolling is instructed by a joy stick 8a, a memory control circuit 9b inside the display ASIC9 judges whether or not the rewrite of the display memory 5 is required, and when it is not required, rewrites the screen just by changing the read start address of the plotting memory 4. On the other hand, when the rewrite of the screen is required, only data for performing rewrite are DMA(direct memory access) transferred from the plotting memory 4 to a FIFO(fart in fast out) memory 9c inside the display ASIC9 and then, the data of the FIFO memory 9c are read at a prescribed timing, stored in the display memory 5 and also transferred to a display control circuit 9c. Thus, at the time of screen rewrite by scrolling, the screen is rewritten without reading the data of the display memory 5 and high-speed scrolling is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen scroll control device capable of scrolling an image displayed on a display device.

[0002]

2. Description of the Related Art Navigation devices capable of displaying road maps in a preset range are known. When this type of device is installed in a vehicle, the installation space inside the vehicle is limited, so the screen size cannot be increased so much and the road map range displayed on one screen is also limited. For this reason, normally, a road map or the like on the screen can be scrolled by a cursor key or a joystick.

[0003]

In order to perform such scrolling, it is necessary to rewrite the display memory (VRAM) according to the scroll range, but the contents of the display memory are the horizontal and vertical synchronizing signals of the display device. Since the data must be read synchronously and periodically, the display memory must be rewritten little by little in the meantime, and it takes time to rewrite the screen. In particular, when a plurality of screens are combined and displayed, or when the screen resolution is high, the memory capacity of the display memory increases, and the time required to rewrite the screen also increases accordingly.

Therefore, if a so-called dual port RAM having two types of input / output ports is used as a display memory and data reading in synchronization with a synchronizing signal and data rewriting according to the scroll range are simultaneously performed, high speed scrolling is possible. Is possible. However, since the cost of the dual port RAM is higher than that of the normal DRAM, it causes an increase in the cost of the device. Especially, the larger the memory capacity of the display memory, the larger the price difference from the case of using the normal DRAM.

An object of the present invention is to provide a screen scroll control device capable of performing screen scroll at high speed without using a special memory.

[0006]

The present invention will be described with reference to FIG. 1 showing an embodiment. In the present invention, the first storage means 4 stores image data to be displayed on a display device 6.
And a second storage unit 5 in which at least a part of the image data stored in the first storage unit 4 is stored and which is periodically read out in synchronization with the horizontal and vertical synchronization signals of the display device 6, A screen scroll control device provided with a video signal conversion means 10 for converting the image data read from the second storage means 5 into a video signal, and an instruction means 8a for instructing scrolling of the image displayed on the display device 6. Applied to
Only when the instruction amount of scrolling exceeds a predetermined amount, transfer control means 9b for transferring the image data of the amount corresponding to the instruction amount from the first storage means 4 to the second storage means 5 and the video signal conversion means 10. The above object is achieved by providing According to a second aspect of the present invention, in the screen scroll control device according to the first aspect, the second storage unit 5 is configured to have a storage area wider than a storage area corresponding to one screen of the display device 6. However, when scrolling into the range of the storage area of the second storage means 5 is instructed, the second storage means 5 is not rewritten and the area outside the storage area of the second storage means 5 is moved. When scrolling is instructed, transfer control means is arranged to transfer only image data not stored in the second storage means 5 from the first storage means 4 to the second storage means 5 and the video signal conversion means 10. 9b. According to a third aspect of the present invention, in the screen scroll control device according to the second aspect, the screen scroll control device is interposed between the first storage means 4 and the second storage means 5, and is read from the first storage means 4. The temporary storage means 9a for temporarily storing the output image data is provided, and when the scrolling out of the storage area of the second storage means 5 is instructed, the temporary storage means 9a runs out of free space. Before the temporary storage means 9
The transfer control means 9b is configured to transfer the image data stored in a to the second storage means 5 and the video signal conversion means 10. According to the invention described in claim 4, in the screen scroll control device according to any one of claims 1 to 3, the data stored in the first storage means 4 is DMA-transferred to the second storage means 5. And a counting means for generating a read address of the second storage means 5, and when scrolling out of the storage area of the second storage means 5 is instructed,
The transfer control means 9b is configured to control the DMA controller 7a according to the count value of the counting means.

[0007]

In the invention described in claim 1, when the instruction amount of the scroll instructed by the instruction means 8a is equal to or less than the predetermined amount, the second storage means 5 is not rewritten and the second storage means 5 is stored. The screen is rewritten according to the instruction amount by changing the read address. On the other hand, when the instruction amount exceeds the predetermined amount, the image data is transferred from the first storage means 4 to the second storage means 5 to rewrite the second storage means 5, and
The image data from the first storage means 4 is transferred to the video signal conversion means 10. In the invention according to claim 2, the storage area of the second storage means 5 is made wider than the storage area corresponding to one screen of the display device 6, and the storage area of the second storage means 5 is set within the range. When scrolling is instructed, the screen is rewritten by changing the read address of the second storage unit 5 without rewriting the second storage unit 5, and goes out of the storage area of the second storage unit 5. When the scrolling is instructed, only the image data not stored in the second storage means 5 is transferred from the first storage means 4 to the second storage means 5, and at the same time, transferred to the video signal conversion means 10. To do. That is, when scrolling is instructed, the image data already stored in the second storage means 5 is used to the maximum extent,
The scroll speed is improved by reading only the minimum necessary image data from the first storage unit 4. Claim 3
In the invention described in, the temporary storage means 9a for temporarily storing the image data read from the first storage means 4 is provided between the first storage means 4 and the second storage means 5. Before the temporary storage means 9a runs out of free space, the image data stored in the temporary storage means 9a is transferred to the second storage means 5 and the video signal conversion means 10. According to the fourth aspect of the invention, the DMA controller 7 is controlled by the count value of the counting means for generating the read address of the second storage means 5.
a is controlled, and a dedicated circuit for controlling the DMA controller 7a is unnecessary.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. It is not limited to.

[0009]

1 is a block diagram of an embodiment of a screen scroll control device according to the present invention. In the present embodiment, an example will be described in which the screen control device is integrally incorporated in the vehicular navigation device.

In FIG. 1, reference numeral 1 denotes a current position detecting device for detecting the current position of the vehicle, for example, a direction sensor for detecting the traveling direction of the vehicle, a vehicle speed sensor for detecting the vehicle speed, and a GP.
It is composed of a GPS sensor and the like for detecting GPS signals from S (Global Positioning System) satellites.

Reference numeral 2 is a map recording medium for storing road map data of a plurality of different map scales. The map recording medium 2 is detachably connected to the reading control device 3, and the reading control device 3 reads the road map data stored in the map recording medium 2 according to an instruction from a CPU described later.

Reference numeral 4 is a drawing memory in which the road map data read by the read control device 3 is temporarily stored, and is usually composed of a DRAM. Reference numeral 5 denotes a display memory that stores image data to be displayed on the display device 6,
This display memory 5 is also composed of DRAM. The image data stored in the display memory 5 is read at a speed synchronized with the horizontal and vertical synchronizing signals of the display device 6 and displayed on the screen.

Reference numeral 7 is a CPU for controlling the entire apparatus, and inside thereof is a DMA from the drawing memory 4 to the display memory 5.
(Direct Memory Access) A DMA controller 7a for controlling transfer is built in. Reference numeral 8 denotes a remote-controlled transmitter that is remotely operated, and its operation information is input to the CPU 7. The remote control transmitter 8 is provided with a joystick 8a capable of instructing scrolling of the screen in addition to various switches for selecting functions.

Reference numeral 9 denotes a display ASIC for controlling data transfer from the drawing memory 4 to the display memory 5, and inside thereof, a FIFO memory 9a for temporarily storing data read from the drawing memory 4 and a FIFO memory 9a. And a memory control circuit 9b for controlling writing / reading to / from the display memory 5, and a display control circuit 9c for synthesizing image data read from the display memory 5 (synthesizing a plurality of screen data) and detecting color information. include. The output of the display control circuit 9c is converted into analog video signals (R, G, B signals) by the D / A converter 10 and sent to the display device 6 for display.

FIG. 2 is a diagram showing a display area of the display memory 5. As shown in the figure, 384 dots in the left and right direction of the screen,
A display area for 252 dots is provided in the vertical direction. Of these, a 320 × 240 dot area indicated by a thick line indicates a range that is actually displayed on the screen, and the surrounding area is used for scrolling. The scroll area is shown. By providing such a scroll area, it becomes unnecessary to frequently rewrite the contents of the display memory 5. For example, in the case of scrolling from the range indicated by the thick line in FIG. 2 to the range indicated by the alternate long and short dash line, this range is within the scroll area, and therefore, simply by changing the read address of the display memory 5 without rewriting the display memory 5. Can be displayed.

FIG. 3 is a flow chart showing an outline of the scroll control processing performed by the memory control circuit 9b in the display ASIC 9, and the operation of this embodiment will be described below based on this flow chart.

In step S1 of FIG. 3, it is determined whether or not scrolling of the screen is instructed by the joystick 8a or the like. When the determination is affirmative, the process proceeds to step S2, and it is determined whether or not scrolling of a range that does not require rewriting of the display memory 5 is instructed. That is, it is determined whether or not scrolling within the scroll area of FIG. 2 is instructed.

When it is determined that the display memory 5 need not be rewritten, the process proceeds to step S3, and the start address is set according to the scroll amount. Here, the start address indicates the start address when reading the display memory 5. In step S4, the data in the display memory 5 is sequentially read from the start address and transferred to the display control circuit 9c in synchronization with the horizontal and vertical synchronizing signals of the display device, and then the process returns to step S1. The data transferred to the display control circuit 9c is subjected to detection of color information and combination with other screen data inside thereof, and then sent to the D / A converter 10 for analog R, G and B data. Converted to a signal.

On the other hand, if the determination in step S2 is negative, that is, if the scrolling of the range in which the display memory 5 needs to be rewritten is instructed, the process proceeds to step S5, and the start address of the display memory 5 is set. , Sends a control signal to the DMA controller 7a to rewrite a part of the display memory 5.

In step S6, for the data within the range already stored in the display memory 5, the display memory 5
From the drawing memory 4 to the FIFO memory 9a by DMA for other data, then read the data in the FIFO memory 9a at a predetermined timing and store it in the display memory 5, and display control is performed. Transfer to circuit 9c.

FIG. 4 is a diagram for explaining the details of the processing in step S6 of FIG. If the area P shown in the figure is a display area including the scroll area, the area Q is a real screen display area before scrolling, and the area R is a screen area after scrolling, the area R
Since the data within the range of 1 (hatched portion in the figure) is already stored in the display memory 5, the data in the display memory 5 is transferred to the display control circuit 9c as it is, and the data within the range of the region R2 is drawn. The data DMA-transferred from the memory 4 to the FIFO memory 9a is stored in the display memory 5 and also transferred to the display control circuit 9c for display.

FIG. 5 is a detailed flowchart of the process of step S6 of FIG. In step S51 of FIG. 5, the initial value of the address counter (not shown) provided inside the display ASIC 9 is set as the start address set in step S5 of FIG. In step S52, it is determined whether or not the horizontal synchronizing signal is input. If not input, the process stays in step S52, and if it is input, step S53.
Proceed to.

In step S53, the address counter is incremented. In step S54, it is determined whether the value of the address counter is within a predetermined range. That is, in step S54, the drawing memory 4
Whether or not to perform the DMA transfer to the O memory 9a is determined by the value of the address counter.

If the value of the address counter is not within the predetermined range, the process proceeds to step S55, and the data in the display memory 5 stored at the address indicated by the address counter value is transferred to the display control circuit 9c. On the other hand, if the value of the address counter is within the predetermined range, step S5
6, the read address information of the drawing memory 4 is set to D
Transfer to the MA controller 7a. Upon receiving this information, the DMA controller 7a reads the data from the drawing memory 4 and DMA-transfers the data to the FIFO memory 9a inside the display ASIC 9. In step S57, the data DMA-transferred from the drawing memory 4 to the FIFO memory 9a is read at a predetermined timing, stored in the display memory 5, and transferred to the display control circuit 9c.

When the process of step S55 or S57 is completed, the process proceeds to step S58, it is determined whether or not the display for one screen is completed, and if it is not completed, step S58 is executed.
Returning to step 52, when the display for one screen is completed, the process returns to step S51.

As described above, in the process of FIG. 5, it is determined whether or not the content of the display memory 5 is rewritten according to the value of the address counter that generates the read address of the display memory 5, and the value of the address counter falls within the predetermined range. Only in this case, the data is DMA-transferred from the drawing memory 4 to the display memory 5.

As described above, in this embodiment, since the display area having a wider area than the area to be actually displayed is provided, the display memory 5 is not rewritten to scroll the display area. The screen can be rewritten at high speed when scrolling. When the contents of the display memory 5 are rewritten, the contents of the display memory 5 are read in order to write the data in the drawing memory 4 into the display memory 5 at high speed by DMA transfer and at the same time to transfer the data to the display control circuit 9c. Can display a new image without
The screen rewriting speed is improved.

Further, in the prior art, a circuit for controlling the DMA controller 7a was separately required, but in the present embodiment, DMA is performed by an address counter inside the display ASIC 9.
Since the controller 7a can be controlled, a dedicated circuit for controlling the DMA controller 7a becomes unnecessary, and the circuit scale can be reduced.

In the above embodiment, the FIFO memory 9a is provided between the drawing memory 4 and the display memory 5 to adjust the timing of reading and writing the data. However, the drawing memory is not provided but the drawing memory 9a. New image data may be directly written from 4 to the display memory 5. Further, the FIFO memory 9a, the memory control circuit 9b and the like may not be stored inside the display ASIC 9 but may be configured by a discrete circuit.

In the embodiment thus constructed, the drawing memory 4 serves as the first storage means, the display memory 5 serves as the second storage means, the D / A converter 10 serves as the video signal conversion means,
The joystick 8a serves as an instruction means and the memory control circuit 9
b corresponds to the transfer control means, and the FIFO memory 9a corresponds to the temporary storage means.

[0031]

As described above in detail, according to the present invention, the second storage means is rewritten only when the scroll instruction amount exceeds the predetermined amount.
The storage means does not have to be rewritten, and the scroll speed is improved. When rewriting the second storage means,
Since the new image data from the first storage means is simultaneously transferred to the video signal conversion means, a new image can be displayed without being read from the second storage means, and the screen rewriting speed is improved. According to the invention of claim 2,
Since the storage area of the second storage means is provided for one screen or more,
When scrolling into the range of the storage area of the second storage means is instructed, the specified range is displayed by simply changing the read address of the second storage means without rewriting the second storage means. it can. That is, when scrolling is instructed, the image data already stored in the second storage means is used to the maximum extent, and only the minimum necessary image data is read out from the first storage means. Scrolling is possible. According to the third aspect of the invention, since the temporary storage means is interposed between the first storage means and the second storage means, the read timing of the first storage means and the second storage means It becomes easier to adjust the timing with the write timing. According to the invention described in claim 4, since the DMA controller is controlled by the count value of the counting means for generating the read address of the second storage means, a circuit for controlling the DMA controller as in the conventional case is not required. The circuit scale can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a screen scroll control device according to the present invention.

FIG. 2 is a diagram showing a display area of a display memory.

FIG. 3 is a flowchart showing an outline of scroll control processing performed by a memory control circuit inside the display ASIC.

FIG. 4 is a diagram for explaining the details of the processing in step S6 of FIG.

5 is a detailed flowchart of the process of step S6 of FIG.

[Explanation of symbols]

 1 Current Location Detection Device 2 Map Recording Medium 3 Reading Control Device 4 Drawing Memory 5 Display Memory 6 Display Device 7 CPU 7a DMA Controller 8 Remote Control Transmitter 8a Joystick 9 Display ASIC 9a FIFO Memory 9b Memory Control Circuit 9c Display Control Circuit 10 D / A converter

Claims (4)

[Claims] 1. A first storage means for storing image data to be displayed on a display device, and at least a part of the image data stored in the first storage means for storing the image data of the display device. A second storage unit that is periodically read in synchronization with horizontal and vertical synchronization signals; a video signal conversion unit that converts the image data read from the second storage unit into a video signal; In a screen scroll control device including an instruction unit for instructing scrolling of a displayed image, only when the instruction amount for scrolling exceeds a predetermined amount, the first storage unit to the second storage unit and the A screen scroll control device, comprising: a transfer control means for causing the video signal conversion means to transfer an amount of image data corresponding to the instructed amount. 2. The screen scroll control device according to claim 1, wherein the second storage means has a storage area wider than a storage area corresponding to one screen of the display device, and the transfer control means When the scrolling within the range of the storage area of the second storage means is instructed, the rewriting of the second storage means is not performed, and scrolling out of the range of the storage area of the second storage means is performed. Screen is characterized in that only image data that is not stored in the second storage means is transferred from the first storage means to the second storage means and the video signal conversion means when is instructed. Scroll control device. 3. The screen scroll control device according to claim 2, wherein an image is provided between the first storage unit and the second storage unit and read from the first storage unit. The transfer control means is provided with a temporary storage means for temporarily storing data, and the transfer control means determines that the free space of the temporary storage means is reduced when scrolling out of the storage area of the second storage means is instructed. A screen scroll control device, characterized in that the image data stored in the temporary storage means is transferred to the second storage means and the video signal conversion means before they disappear. 4. The screen scroll control device according to claim 1, wherein the data stored in the first storage means is stored in the second storage device.
And a counting means for generating a read address of the second storage means, wherein the transfer control means scrolls out of the storage area of the second storage means. The screen scroll control device, wherein the DMA controller is controlled according to the count value of the counting means when the instruction is given.