JPS62105189A - Display control system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a display control system, and more particularly, to a method for outputting control information, which provides various control information in addition to image data when displaying an image.

[Conventional technology]

A CRT display is equipped with a display memory and its control device, and displays various figures on a CRT (cathode ray tube) by sending image data from the display memory.

At this time, the display control device gives an address to the display memory, but also performs processing such as filling in figures.
This is done by returning the results to the display memory.

[Problem that the invention seeks to solve]

During display, the display control device also outputs various control information such as multi-window switching, multi-window color specification, window bank color, window type (character screen or graphic screen, etc.), scrolling and zooming, etc. .

Conventionally, control information has been output during a blanking period (more specifically, during a predetermined period in the middle of the blanking period excluding before and after the synchronization signal), but this period is narrow (therefore, when the amount of control information becomes large, it becomes difficult to output the control information. External storage circuitry is required so that the information is available during the display period.

The present invention aims to improve these points, reduce the number of external circuits, and reduce costs and space.

[Means for solving problems]

The present invention provides a display control method for a display system including a display memory that stores image data of a CRT display, and a display control device that reads and writes data from the memory and outputs control information. The control information output bus is connected to the data bus via a buffer, and the control information output bus is connected to the data bus of the display control device via a latch, and during the display read cycle and the drawing calculation cycle that are alternately repeated. The display control device is characterized in that it outputs display control information through a data bus of a vacant display control device and causes the latch to latch the display control information.

[Effect]

Reading during display is performed by the display control device inputting an address to the display memory and reading out the contents of the display memory at the address, but the read data is sent to the CRT and is not taken in by the display control device. Therefore, during reading during display, the data bus of the display control device becomes empty. The present invention utilizes this vacant data bus to output various control information.

〔Example〕

To explain it with the drawings, in FIG. 1, 10 is a display memory, 12 is a display control device, 14 is an address bus, and 16 is a table display memory readout and a CRT (not shown) (more specifically, a parallel/serial converter placed in front of it). data bus, 18 is this bus 1
6 is a data bus of the display control device connected via a buffer (gate) 20, 22 is a control information latch connected to the bus 18, and 24 is a data bus for outputting control information. The display memory 10 and display control device 12 are LS
I and is attached to a printed circuit board on which buses 16, 18, etc. are formed.

During display, display controller 12 sends an address to display memory 10 via bus 14, and the display memory contents at that address are sent to CRT via bus 16. When performing drawing operations such as filling in figures, drawing lines, displaying triangles or rectangles, the display control device 12 sends an address to the display memory 10 through the bus 14, reads out the display memory contents at the address, and transfers them to the bus 16, buffer 20. It is taken in through the bus 18 and subjected to arithmetic processing such as AND-OR and exclusive-OR, and the processing results are returned (written) to the display memory 10 through the bus 18, buffer 20, and bus 16.

Display reading and drawing calculations are performed alternately. Since the bus 18 is not used during display reading, the present invention outputs control information through the bus 18, latch 22, and bus 24 during this period.

The display/drawing in FIG. 2 shows that display reading and drawing operations are performed alternately. The addresses that the display controller sends to the display memory are for these. data bus 1
The display memory read data output to 6 is, for example, in 16-bit units (32-bit units, 64-bit units, etc.), and these data are sent to the parallel/serial converter mentioned above and converted into a serial signal. The signal is then added with horizontal and vertical synchronization signals to become a CRT video signal. Read data at the time of drawing calculation is sent to the display control device 12,
Arithmetic processing is performed here and then written to the display memory 10. This writing may be performed in the next drawing calculation cycle; in this case, reading is performed in the drawing calculation cycle, calculation is performed in the next display readout cycle, and writing is performed in the next drawing calculation cycle. Display controller 12 also outputs control information to data bus 18 during display read cycles, which is latched into latch 22 and sent out over bus 24.

One line (one horizontal scanning line) of a CRT display has, for example, 1024 bits, and if the number of bits of read data in a display read cycle is 16, the display is read out 64 times to output data for one line. In the case of color display, one dot is represented by 4 bits, so the number of readings is 4.
Double or number of data buses (number of bits read simultaneously)
Take a method such as quadrupling the amount.

In the case of a multi-window display, the display memory 10 stores data for each window. Assuming that there are three windows A, B, and C, these windows may overlap, and in this case, the data of the window at the top is displayed, and the data of the window that overlaps at the back is not displayed.

This selection of display data can be performed by changing the display memory 10 access address output by the display control device 12 in synchronization with the scanning of the CRT. For example, data for each window can be stored at a different address in the display memory. This can be done by switching the address to read the data of the front window in the overlapping part, but in the display memory, one screen is set as one window, so that the data of these three types of screens can be read at the same time at the same address. You may also select the data externally. In the latter case, the display control device 12 sends a data selection signal (this is one type of control information) at the window overlap portion to instruct which window data should be selected and displayed.

Drawing operations change the display screen data,
If this is incremented during each display readout cycle, the display screen data can be changed without interfering with the display on the CRT and without any particular timing delay. Further, in FIG. 2, the display readout period and the drawing calculation period are shown as having the same time length, but this may be changed as appropriate, such as making the former shorter and the latter longer. Furthermore, the drawing cycles and the display cycles do not necessarily have to be alternate, but as long as they are exclusive, the display or drawing may be continuous.

Further, for the sake of explanation, the display control device has been explained separately into an address bus and a data bus, but the same effect can be obtained even if addresses/data are outputted to the display memory from the same terminal in a time-sharing manner.

〔Effect of the invention〕

As explained above, in the present invention, the display control device outputs various control information using the vacant data bus during the display readout period, so that sufficient time is obtained for outputting the control information, and Unlike the system that outputs control information during the blanking period, there is no need for a device to store control information, and external attachment can reduce the number of circuits, reduce costs, and save space.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart 1 for explaining the operation. In the drawing, 10 is a display memory, 12 is a display control device, 16 is a data bus of the display memory, 18 is a data bus of the display control device, 20 is a buffer, 22 is a latch, and 24 is a control information output bus.

Claims (1)

[Scope of Claims] A display control method for a display system including a display memory that stores image data of a CRT display, and a display control device that reads and writes data from the memory and outputs control information, comprising: a data bus of the display memory and display control. A control information output bus is connected to the data bus of the device via a buffer, and a control information output bus is connected to the data bus of the display control device via a latch, and the display read cycle of the display read cycle and the drawing calculation cycle that are exclusively repeated. During the period, the display control device
A display control method characterized by outputting display control information through a data bus of a vacant display control device and causing the latch to latch the display control information.