JPH027476B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a microcomputer incorporating a display drive circuit that directly drives a display device.

(B) Prior Art In recent years, among 4-bit or 8-bit one-chip microcomputers, microcomputers incorporating a liquid crystal drive circuit capable of directly driving a display device, particularly a liquid crystal display device, have been developed. As shown in FIG. 1, such a microcomputer is provided with a display memory circuit 2 for applying display data to a segment drive circuit 1, and a display memory circuit 2 for applying display data to a segment drive circuit 1. The display is made by transferring the information. Previously, the operand of the display command
Data was transferred by directly specifying the address of the RAM and the address of the display memory circuit 2. That is, the address of RAM 3 is specified by the data X set in the code of the display command, and the data stored at that address is displayed as specified by the data Y set in the code of the display command. The data is transferred to the address in the memory circuit 2 for use. Therefore, if all the displays are to be rewritten, display commands must be executed for the number of addresses in the display memory circuit 2, so if there are many displays, the number of program steps will increase, making it difficult to create a program. It had the disadvantage of low efficiency.

(C) Purpose of the Invention The present invention has been made in view of the above-mentioned points, and enables the creation of a display program efficiently by making it possible to specify the address of a display memory circuit using a strobe pointer. Furthermore, the purpose is to make it easy to create.

(d) Structure of the Invention The present invention includes a display drive circuit that directly drives a display device, and a display storage circuit that stores display data corresponding to a segment and applies the display data to the display drive circuit. In the microcomputer, when a predetermined instruction is executed, a strobe pointer that takes in data indicating the address of the display storage circuit sent to the data bus, and decodes the output of the strobe pointer;
This configuration includes a strobe decoder that applies a strobe signal to the display memory circuit when a display data write command is executed.

(E) Embodiment FIG. 2 is a block diagram of a microcomputer showing an embodiment of the present invention. The ROM 4 is a storage circuit that permanently stores programs, and programmed instructions are sequentially applied to the control circuit 5. The picture control circuit 5 decodes the applied command and controls various circuits to execute the command. 4
A data bus 6 consisting of bits includes an ALU 7,
RAM 8, data pointer 9, segment decoder 10, strobe pointer 11, etc. are connected,
Data is sent and received between each circuit via the data bus 6. The ALU 7 is an arithmetic processing unit and performs processing such as addition or subtraction of data. RAM
8 is a storage circuit that stores data and can retrieve the data as needed; its address is the content stored in the data pointer 9 or the operand of the instruction Gord output from the ROM 4. It is specified. data pointer 9
is a register that stores data sent to the data bus 6 as necessary, and the address of the RAM 8 can be specified by the stored data. Segment decoder 10 connects data bus 6
For example, the 4-bit BCD code sent to
It is converted into seven segment signals for numerical display and applied to the display memory circuit 12. The display memory circuit 12 has memory elements each corresponding to a segment that can be driven by the segment drive circuit 13 , and the segment drive circuit 13 uses the contents stored in the memory elements of the display memory circuit 12 ,
Create a segment drive signal to drive the segment. This segment drive circuit 13
is, for example, a circuit for driving a liquid crystal display device. Further, the address of the display memory circuit 12 is specified by the strobe pointer 11. That is, when data taken into the strobe pointer 11 via the data bus 6 is decoded by the strobe decoder 14 and an instruction for writing the data into the display storage circuit 12 is executed,
A plurality of strobe signals are created and applied to the display storage circuit 12. This strobe signal specifies the storage element into which the data sent to the data bus 6 and converted by the segment decoder 10 is to be written, and the display data is stored.

FIG. 3 is a circuit diagram showing some of the blocks shown in FIG. 2. Data bus 6 is DBUS0~3
DBUS0 to DBUS3 are connected to the segment decoder 10. The segment decoder 10 converts the 4-bit BCD code sent to DBUS0-3 into segment signals a-g for numerical display and outputs them. The strobe pointer 11 consists of four latch circuits 15, each input terminal L is applied with a corresponding bit signal DBUS0 to DBUS3 of the data bus 6, and a clock terminal φ receives a predetermined command, such as MRSB. A control signal output from the control circuit 5 shown in FIG. 1 when an instruction (an instruction to transfer the data stored in the RAM address specified by the operand of this instruction to the strobe pointer 11) is executed.
MSP is commonly applied. That is, when the MRSB instruction is executed, the 4-bit data stored in RAM 8 is stored in strobe pointer 11.

The strobe decoder 14 consists of eight NAND gates 16 and eight NAND gates 17.
NAND gate 16 has strobe pointer 1
1 latch circuit 15 output Q and inverter 18
a signal inverted by is selectively applied,
In addition, when a WRT instruction for writing display data to the display memory circuit 12 is executed, all NAND gates 16 are connected to the control circuit 5 shown in FIG.
A control signal WRT output from the two is commonly applied. Furthermore, each output of the NAND gate 16 is
applied to one input of the NAND gate 17,
Further, an initial clear signal is commonly applied to the other input of the NAND gate 17,
The outputs of the NAND gates 17 are output as strobe signals STB0 to STB7, respectively. That is, if the initial clear signal becomes "0" when the power is turned on, all strobe signals STB0 to STB7 become "1", and when the WRT command is executed, the control signal WRT becomes "1". Then, depending on the state of the output of the latch circuit 15, the strobe signal
Any one of STB0 to STB3 becomes "1", and any one of strobe signals STB4 to STB7 becomes "1". This strobe signal
Display memory circuit 1 by combination of STB0 to STB7
Storage in the second storage element is controlled.

The display memory circuit 12 includes the segment drive circuit 1
The latch circuit 19 is a storage element corresponding to each segment that can be driven by the latch circuit 19, and a NAND gate 20 whose output is connected to the clock terminal φ of each latch circuit 19.
The input of the NAND gate 20 has a strobe signal.
Any one of STB0 to STB3 and any one of strobe signals STB4 to STB7 are selectively applied, and the address of the selected latch circuit 19 is determined by the combination. , and the input L of the latch circuit 19 receives segment signals a to g output from the segment decoder 10.
are selectively connected. That is, the input L of the latch circuit 19 is connected to segment signals a to g from which the display data of the segment corresponding to the latch circuit 19 is output. For example, a latch circuit 19 that stores segment display data for one digit for numerical display is all connected to the same strobe signal as one address, and segment signals a to g for each are connected to the inputs of the latch circuit 19. Ru. Further, the outputs Q of the latch circuits 19 are respectively applied to segment drive circuits 13, and the segment drive circuits 13 generate signals for driving the segments based on the contents of the applied outputs Q, for example, when driving a liquid crystal. Create a liquid crystal drive signal and connect it to output terminal 2.
Output from 1.

Therefore, according to the configuration shown in FIG. 3, the address of the display memory circuit 12 is specified by the contents of the 4-bit data stored in the strobe pointer 11, and is specified by the write command, that is, the WRT command. The display data is stored at the specified address.

In this way, in a microcomputer configured as shown in FIGS. 2 and 3, when a clock is created by a program and the time is displayed, the RAM 8 is stored as shown in FIG. 10 o'clock data in address "0", hour data in address "1",
10 minute data is stored at address "2" and minute data is stored at address "3". On the other hand, address "0" of the display memory circuit 12 is the memory element corresponding to the 10 o'clock segment, and address "1" is the hour data. The memory element corresponding to the digit segment, address "2", is set to include the memory element corresponding to the ten minute segment, and the address "3" is set to include the memory element corresponding to the minute segment. When displaying, the data pointer 9 first specifies the address "0" of the RAM 8, and the strobe pointer 11 first specifies the address "0" of the display memory circuit 12. . and RAM by WRT command
The data stored at address "0" of 8 is transferred to address "0" of display storage circuit 12. After that, data pointer 9 and strobe pointer 1
Add "1" to the contents of 1 and execute the WRT instruction. Display data is written by repeating this operation four times.

The above-mentioned operation is shown in the flow diagram of FIG. 5, and the operation will be explained using FIGS. 2 and 3. The display program first sets initial values to the data pointer 9 and strobe pointer 11, and then loads the RAM 8.
and designates the initial address of the display storage circuit 12. Then, by executing the WRT command, the data stored in the address of RAM 8 specified by the data pointer 9 is applied to the segment decoder 10 via the data bus 6, while the control signal
Strobe signal depending on WRT timing
STB0~7 are output and strobe pointer 11
The converted segment signals a to latch circuit 19 at the address of the display storage circuit 12 specified by
g is memorized. Next, "1" is added to the data pointer 9 and strobe pointer 11, and further,
It is determined whether the addition result has reached a predetermined value "A". If it is not the predetermined value "A", it means that all the display data has not been written yet,
Execute the WRT command again. Then, when the predetermined value "A" (A=4 in the case of FIG. 4) is reached, the display program ends. Therefore, unlike conventional methods, there is no need to line up write commands by the number of digits displayed, and the program can be formed into a loop.
The program will be shorter.

(F) Effects of the Invention As described above, according to the present invention, since the address of the display memory circuit can be changed by addition or subtraction of the strobe pointer, the display program can be formed in a loop shape, and the program can be short and ,
It becomes easy. In particular, change the display and everything,
To turn on or off all segments,
The effect is remarkable.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional example, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a circuit diagram showing a part of the block shown in FIG. 2, and FIG. 5 is a diagram showing an example of time display, and FIG. 5 is a flow diagram showing a display program. Explanation of main drawing numbers, 4...ROM, 5...control circuit,
6...Data bus, 7...ALU, 8...RAM, 9...Data pointer, 10...Segment decoder, 11
...Strobe pointer, 12...Display memory circuit,
13... Segment drive circuit, 14... Strobe decoder.

Claims (1)

[Claims] 1. In a microcomputer equipped with a display drive circuit that directly drives a display device, and a display storage circuit that stores display data corresponding to a segment and applies the display data to the display drive circuit,
When a predetermined instruction is executed, a strobe pointer that takes in data indicating the address of the display storage circuit sent to the data bus, and an output of the strobe pointer is decoded, and when a display data write instruction is executed. , and a strobe decoder for applying a strobe signal to the display memory circuit.