JPH04112280A - Display controlling circuit and microcomputer provided with the same - Google Patents

Abstract

PURPOSE:To enable the simultaneous display of a graphic display and a character display by one chip by presetting data indicating the boundary of display parts, counting data indicating present display positions, an operating the coincident comparison of the preset data and the counted data in order to switch and output read-out data. CONSTITUTION:Data AD1-ADn indicating the part being the boundary of a displaying panel 2 are preset in a register 4, at the time of operating the simultaneous display of the graphic display and the character display at the displaying panel 2. A counter 6 counts the number of lines in the vertical direction at the displaying panel, and a comparator 7 compares the preset data of the register 4 with the counted data of the register 6 in order to operate a coincident detection. Then, the read-out data of either a display RAM 1 or a character generator ROM 3 are switched and outputted, based on the output signals of the comparator 7 and control signals to operate the simultaneous display at the displaying panel 2. Thus, the simultaneous display of the graphic display and the character display can be operated by one chip.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a display control circuit and a microcomputer equipped with the same, and particularly to a display control circuit for simultaneously displaying graphics and characters on a display panel such as an LCD. The present invention relates to a suitable display control circuit and a microcomputer equipped with the same.

(b) Conventional technology Conventionally, in a one-chip microcomputer
When displaying predetermined characters on a display panel such as D, either a graphic display or a character display is only displayed alternately, and both cannot be displayed at the same time. A prior art technology for such a one-chip microcomputer is disclosed in Japanese Patent Application No. 63-286043. That is, according to the microcomputer shown in Japanese Patent Application No. 63-286043, one bit of data is stored in one part of the display panel.
A display RAM that stores display data for so-called graphic display corresponding to lighting/extinguishing of dots or character codes for character display, and a character generator R that can store display data for character display.
It has a built-in OM. When the microcomputer is used for graphic display, the display R
The AM is allowed to store display data for graphic display, and predetermined characters are displayed on the display panel using display data readable from a designated address in the display RAM. On the other hand, when the microcomputer is used for character display, address data for accessing the address of the character generator ROM, so-called character codes, is stored in the display RAM, and the character code read from the designated address of the display RAM is stored in the display RAM. The designated address of the character generator ROM is accessed at #, and a predetermined character is displayed on the display panel based on the display data read out from the character generator ROM at this time.

(c) Problems to be Solved by the Invention However, in the conventional technology, since the control methods for graphic display and character display are different, it has not been possible to display both at the same time with a single-chip microcomputer. Therefore, depending on current needs (for example, simultaneous display of graphic equalizer level display and frequency character display corresponding to each level), two microcomputers are required to display both at the same time. Therefore, there was a problem that the cost was high.

Furthermore, if you try to perform both displays using a single-chip microcomputer and use only the graphic display, you will have to match 1 bit data in the display RAM to 1 dot on the display panel to display characters. There was a problem in that the storage capacity of the display RAM was extremely large and the chip became large. Furthermore, there is a problem in that the program steps are long and the display takes time.

Also, if you try to perform both displays on a single-chip microcomputer and use only character display,
There has been a problem that the number of types of character patterns that can be stored in the character generator ROM increases, and the storage capacity of the character generator ROM becomes limited.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microcomputer that can simultaneously display graphics and characters on a single chip.

(2) Means for Solving the Problems The present invention has been achieved in order to solve the above-mentioned problems, and includes a display RAM that stores display data for graphic display and a display for character display. a character generator ROM in which data is stored, and displays read data from the display RAM or the character generator ROM on a display panel; a register that can be preset with data indicating the current display position of the display panel; a counter that sequentially counts data indicating the current display position of the display panel; a comparator that compares the preset data of the register with the count data of the counter; and an output signal of the comparator. , a control signal for causing the display panel to display graphics and characters at the same time, the display RAM or the character generator RO
The present invention is characterized by comprising a switching circuit that switches and outputs M read data. Further, the present invention is characterized in that this display control circuit is provided in a microcomputer.

(*) Function According to the present invention, simultaneous display of graphics and characters can be performed on the display panel using only one display control circuit or a one-chip microcomputer incorporating this display control circuit. .

(f) Example The details of the present invention will be specifically explained with reference to the drawings. In this embodiment, it is assumed that the display control circuit is built into the microcomputer.

The drawings illustrate embodiments of the invention.

In the drawing, (1) is a display RAM, and the display RAM
A display panel such as an LCD (
The display data in which 1 bit data corresponds to 1 dot in 2) is completely stored, and the remaining predetermined addresses of the display RAM (1) are filled with character generator ROM (3), which will be described later.
) is assumed to have been memorized. In the character generator ROM (3),
Display data for displaying predetermined characters on the display panel (2) is stored, and the character generator ROM (3)
The predetermined address of is accessed by a character hood stored in the display RAM (1). That is, the display data of the character generator ROM (3) and the character code of the display RAM (1) correspond to the character desired to be displayed at the specified position on the display panel (2). (4) is a latch circuit (5-
This is a register consisting of 1) to (5-n), and the register (4) contains the part that becomes the boundary of the display panel (2) when displaying the display panel (2) at the same time as a graphic display and a character display. (e.g. number of vertical lines) n
Bit data AD1 to ADn are preset. Further, it is assumed that the data ADZ to ADn can be latched by the latch circuits <5-1) to (5-n) by the clock CK2.

(6> is an n-bit counter, and the counter (6)
counts the number of vertical lines on the display panel (2). (7) is a comparator and register (4
) and the count data of the counter (6) to detect a match, and when both data match, a match output "1" is output.

(8) is a flip-flop consisting of NOR gates (9) and (10), and one input of the NOR gate (9) is applied with a reset signal R3T which becomes 11'' at the initial time, and one of the inputs of the NOR gate (10) is The output of the comparator (7) is applied to the input of the . (11) is a latch circuit, and when the display panel (2) is to display graphics and characters at the same time, the latch circuit (11) is connected to the latch circuit (11). When displaying one of the two, the control signal sI that becomes "0." is latched. (12) is a latch circuit, and the latch circuit (12) is connected to the display panel (
2), a control signal S is latched, which is "O" for graphic display and "1." for character display. These latch circuits (11) (12) ) latches the control signals S, S, based on the clock CKI. (
13) is a switching circuit for switching between graphic display and character display above and below the boundary in the display panel (2), and the switching circuit (13) is connected to AND gates (14) (15) and OR gate (16). ), and transfer gates (17-1) to (17-m) and (1) that switch and output the read data of the display RAM (1) and character generator ROM (2).
B-1) (18-m) and the transfer gate (17-m)
-1) ~ (17-m), (18-1) ~ (18-m)
It consists of an inverter (19) for switching the operation. In addition, the display RAM (1) and the character shenet t, -4
The read data of ROM (3) is assumed to be m bits. (
20) is a segment drive circuit, and display RAM (1)
or a state in which data read from the character generator ROM (3) can be displayed on the display panel (2);
It is assumed that up to the output of the segment drive circuit (20) is built into a one-chip microcomputer, and the common drive circuit is omitted for the sake of explanation.

Now, the operation will be explained based on the drawings.

For example, a case will be described in which the center of the vertical line of the display panel (2) is set as the boundary between the graphic display and the character display, and the character display is displayed in the upper half and the graphic display is simultaneously displayed in the lower half. In this case, the latch circuit (
11), the control signal SI of "1" is latched by the clock CKI, and the latch circuit M constituting the register (4)
In (5-1) to (5-n), n-bit data indicating the boundary of the display panel (2>) is latched.Furthermore, the flip-flop (8) is initial reset by the reset signal R8T of "1". In other words, only transfer gates (18-1) to (18-m) are open.

Then, a predetermined address of the character generator ROM (3) is accessed by the character hood of the display RAM (1), and the display data read from the character generator ROM (3) is sent to the segment drive circuit (20).
When the display panel (2) starts to be completely displayed via the display panel (2), the counter (6) starts sequentially counting the number of vertical lines on the display panel (2). After that, when the n-bit data fully latched in the register <4) and the count data of the counter (6) match, that is, when the character display on the display panel (2) reaches the boundary, the comparator (7) outputs - As a result, "1." is output and the flip-flop (8) is set. As a result, a set output of "10" is obtained from the flip-flop (8), and the OR gate (
16) to 10. An output is obtained, and now only the transfer gates (17-1) to (17-m) are opened. Then, the display data read from the predetermined address of the display RAM (1) can be displayed on the display panel via the segment drive circuit (20). This allows character display and graphic display to be displayed simultaneously on the display panel (2). At this time, since one input of the AND gate (15) is set to rO by the Q output of the latch circuit (11), the control signal S can be in any state. Contrary to the above explanation, if the upper part of the border of the display panel (2) is to be displayed as a graphic and the lower part of the border is to be displayed as a character, the inverter (19) is connected to the output of the AND gate (16) and the transfer gate (18-1). ) to (18-m).

Next, when the display panel (2) is to display only graphics or only characters, the control signal S is set to "0".
” and the control signal S may be respectively set to “0” and “1” depending on the graphic display/character display. As a result, the output of the flip-flop (8) becomes the AND gate (14).
), and since the AND gate (15) is open, the display panel (
2) Only graphic display or only character display is performed.

From the above, it is possible to easily display graphics and characters simultaneously on the display panel (2) using only a single-chip microcomputer, thereby reducing costs and reducing the length of program steps. It is possible to perform quick display with reduced display R.
This makes it possible to prevent the memory capacity of the AM (1) and character generator ROM (3) from becoming too large, thereby preventing an increase in the number of chips.

(G) Effects of the Invention According to the present invention, it is possible to easily display graphics and characters simultaneously on a display panel using only one display control circuit or a one-chip microcomputer equipped with this display control circuit. become. As a result, cost increases can be suppressed, program steps can be prevented from becoming long and display can be performed quickly, and the storage capacity of the display RAM and character generator ROM can be suppressed from becoming large and the chip size can be reduced. Advantages such as being able to prevent the increase in the amount of water are obtained.

[Brief explanation of the drawing]

The drawings are diagrams showing embodiments of the invention. (1)...Display RAM, (2)...Display panel,
(3)...Character generator ROM, (4
)...Register, (6)...Counter, (7)...
-Comparator, (13)...switching circuit.

Claims (3)

[Claims] (1) Comprising a display RAM storing display data for displaying graphics and a character generator ROM storing display data for displaying characters,
The display RAM or the character generator ROM
A display control circuit that displays readout data on a display panel includes a register in which data indicating a boundary between a graphic display portion and a character display portion of the display panel is preset, and data indicating a current display position of the display panel. a counter for counting; a comparator for comparing the preset data of the register with the count data of the counter; an output signal of the comparator; and a control signal for displaying a graphic display and a character display on the display panel at the same time. and a switching circuit that switches and outputs read data from the display RAM or the character generator ROM based on the following. (2) The switching circuit receives the output signal of the comparator, a first control signal for making the display panel display a graphic display and a character display simultaneously, and a predetermined display position on the display panel for displaying a graphic display or a character display. 2. The display control circuit according to claim 1, wherein the display control circuit switches and outputs read data from the display RAM or the character generator ROM based on a second control signal for controlling the display RAM or the character generator ROM. (3) A microcomputer comprising the display control circuit according to claim (1).