JPS5926968B2 - Display device control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for display devices such as CRT, EL, liquid crystal, and plasma that do not have a memory function, that is, require refreshment, and in particular, to reduce the time required for transfer, This increases the control time.

Furthermore, cursor information can be controlled simply by inputting it in a program. A device using a display section that requires refreshing requires a memory with a capacity equal to or larger than one screen in order to refresh the screen. The first control method for such a display device is to use a general-purpose IC to configure a dedicated control logic circuit, and the second is to use a microprocessor unit (MPU) as a control device and control input/output devices ( The input/output port (I/O) is one of the input/output ports (I/O).
/0 port), and thirdly, the MPU is used as a control device and at the same time the R of the main memory for the MPU is controlled.
It is conceivable that a part of the AM is used as a refresh memory for display, and each time a character is displayed, the RAM is directly accessed to transfer the character code to the display section and display the character pattern. However, although the first method described above is good when used in large quantities for a single purpose, this type of display device is generally used in small quantities for multiple purposes, and in that case it lacks flexibility. Become. The second method is to control the display device through the I/O port in the same way as other input/output devices, and although it is flexible when the purpose is different, each time the purpose changes, the display device is controlled through the I/O port. It is necessary to send the display information to the display unit through the display, which is very complicated to use. In addition, the third method uses a part of the RAM for the MPU as refresh memory, so if the changed part is corrected, the RAM contents can be transferred directly from the display, so there is no need to transfer them one by one with a program. It's extremely convenient. However, each time a character pattern is displayed on the screen, a character code must be sent to the display unit, and while the character code is being transferred, the MPU is usually unable to use the RAM. , and during that time, I/O unrelated to display
cannot be controlled. Therefore, in the third method, transfer is performed frequently, so there is a drawback that there is less time to control other input/output devices (I/O). Figure 1 is the 3rd figure above.
1 shows a block diagram of a device implementing the control method of M
A control device consisting of a PU, 2 a main memo 18 for the control device consisting of a RAM, 3 a display device, 4 a display unit such as CRT, EL plasma, liquid crystal, etc., 5 other input/output (1/O) devices, 6 is a common bus circuit, and 7 is a signal line through which the display device 3 directly accesses the main memory 2.

In the control device having this configuration, the structure of the conventional display device 3 that directly accesses the main memory 2 is configured as shown in FIG. That is, 11 is a signal line for transferring display data from the main memory 2 to the display device 3, and 12 is a character pattern for converting a character code signal obtained from the main memory 2 into a display character pattern signal suitable for the display unit 4. Generators (C, G), 13 are signal lines for transferring character pattern signals to the display section 3, 14 is a counter for specifying a read address from the main memory 2, 15 is a signal line for transmitting the output from the read counter 14 to the main memory This is a signal line that transfers data to 2. As is clear from this figure, since the character code signal from the main memory 2 is directly input to the character pattern generator 12, display data is transferred from the memory 2 each time a character pattern is scanned to display it. There must be. Since the main memory 2 cannot be accessed from the control device 1 during this transfer, it is not possible to control other input/output devices during this time, and in the end, the more time there is for transfer, the more other devices can be controlled. less time. Further, control signals such as cursor information are transferred from the control device 1 through the signal bus circuit 6, but it is necessary to write them every time they change, which is complicated. The present invention overcomes the above-mentioned drawbacks in the third method, by providing a memory for one line of display characters in the display section to reduce the number of character code transfers,
The transfer time is shortened and the control time for other I/Os is increased accordingly.

In addition, the present invention sets a cursor register RAM at a specific address of the MPU RAM, uses the information in the program, and also uses its output and refresh RAM.
A signal that matches the output of the read counter is sent to the display section at the same time as the character code is transferred, thereby controlling the cursor.

FIG. 3 shows a block diagram of an embodiment of a device implementing the control method of the present invention, in which 21 is a main memory consisting of a RAM partially including memory for refresh and cursor;
3/ is a display device having a register for storing one line of display characters and a timing circuit section.

Since the other components are the same as those in FIG. 1, they are given the same reference numerals and their description will be omitted. FIG. 4 is a circuit diagram showing parts of the main memory 2' and display device 3' that are necessary for explanation. In the diagram, the diagonally shaded wiring connecting each component indicates that the wiring is composed of a plurality of wires. In this figure, 21 is the RAM portion of the main memory 2';
2 is a cursor register (
CR), 23 is a read counter that specifies a read address when reading display data from the RAM portion 21, and 24 is a read counter that compares the output line 25 from the cursor register (CR) 22 with the output line 26 from the read counter 23. 27 is a line connecting the control device 1 and the RAM 2l; 28 is a line connecting the control device 1 and the cursor register 22;
This is the line that connects the The RAM 21 and the cursor register 22 can be freely accessed from the control device 1 through lines 27 and 28. In the display device 3, numeral 31 is a register for one line of display characters that stores the character code from the RAM 2l and the match signal from the comparator 24 on a line-by-line basis. This register 31 is composed of a semiconductor RAM1 shift register (SR). 32
are the read counter 23, the one-line display character register 31. This is a timing circuit section that supplies timing signals to the character pattern generator (CG) 12 and others via a line 33.

Therefore, according to this circuit, the control device 1 can freely change the contents of the RAM 21 and the cursor register 22 using a program.

Furthermore, just by making this change, the display data and cursor coincidence signal can be transferred from the main memory 2' to the display device 3/ by direct access regardless of the program. In addition, since the display device 3' has a register 31 for one line of display characters, if the display character code for each line is transferred from the RAM 2l to the register 31, the character code is transferred every scan until the display of the character pattern for one line is completed. Therefore, the transfer time is shortened, and more time is available for controlling other input/output devices. Furthermore, cursor control information can be controlled simply by inputting the program to a specific address.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram of a circuit implementing a conventional display device control method, and Fig. 2 is a detailed view of the main part of Fig. 1. Fig. 3 is a display device control method according to the present invention. FIG. 4 is a detailed circuit diagram of the main part of FIG. 3. 1: Control device, 2': Main memory, 3': Display device, 4: Display section, 21: RAM section, 22: Cursor register, 23: Read register, 24: Comparator,
31: Register for one line of display characters.

Claims (1)

[Scope of Claims] 1. Using a refresh type display unit and sharing a part of the memory of the control device as memory for refreshing,
A control method for a display device that transfers display data through direct access, characterized in that the display device is provided with a memory for storing one line of the display screen, and a character code for each line is transferred each time one line is displayed in the memory. Display device control method. 2. In the display device control method described in claim 1 above, a part of the memory of the control device is shared as a register for specifying the cursor position, and the output of the register and the counter output for reading the refresh memory are A control method for a display device characterized by controlling a cursor using a coincidence signal.