Design of single chip microcomputer in dynamic digital display circuit

　　1. Experimental tasks

　　As shown in the figure, the P0 port is connected to the character code pen segment of the dynamic digital tube, the P2 port is connected to the digit selection end of the dynamic digital tube, and P1.7 is connected to a switch. When the switch is connected to a high level, "12345" is displayed; when the switch is connected to a low level, "HELLO" is displayed.

　　2. Circuit diagram

　　3. Hardware connections on the system board

　　(1. Connect P0.0/AD0-P0.7/AD7 in the "MCU System" area to ports a-h in the "Dynamic Digital Display" area using an 8-core cable;

　　(2. Connect P2.0/A8-P2.7/A15 in the "MCU System" area to the S1-S8 ports in the "Dynamic Digital Display" area using an 8-core cable;

　　(3. Connect the P1.7 port in the "MCU System" area to the SP1 port in the "Standalone Keyboard" area with a wire;

　　4. Programming content

　　(1. Dynamic scanning method

　　The dynamic interface uses a method in which each digital tube is displayed in turn in a cycle. When the frequency of the cyclic display is high, the flickering display phenomenon cannot be seen by utilizing the retention characteristics of the human eye. This display requires one interface to complete the output of the glyph code (glyph selection) and another interface to complete the lighting of each digital tube in turn (digit selection).

　　(2. When performing digital display, 8 display buffers should be opened for the display unit, and each display buffer is loaded with different display data.

　　(3. For the displayed glyph code data, we use the table lookup method to complete it.

　　5. Flowchart

　　6. Assembly source program

　　ORG 00H

　　START: JB P1.7,DIR1

　　MOV DPTR,#TABLE1

　　SJMP DIR

　　DIR1: MOV DPTR,#TABLE2

　　DIR: MOV R0,#00H

　　MOV R1,#01H

　　NEXT: MOV A,R0

　　MOVC A,@A+DPTR

　　MOV P0,A

　　MOV A,R1

　　MOV P2,A

　　LCALL DAY

　　INC R0

　　RL A

　　MOV R1,A

　　CJNE R1,#0DFH,NEXT

　　SJMP START

　　DAY: MOV R6,#4

　　D1: MOV R7,#248

　　DJNZ R7,$[page]

　　DJNZ R6,D1

　　RET

　　TABLE1: DB 06H,5BH,4FH,66H,6DH

　　TABLE2: DB 78H,79H,38H,38H,3FH

　　END

　　7. C language source program

　　#include

　　unsigned char code table1[]={0x06,0x5b,0x4f,0x66,0x6d};

　　unsigned char code table2[]={0x78,0x79,0x38,0x38,0x3f};

　　unsigned char i;

　　unsigned char a,b;

　　unsigned char temp;

　　void main(void)

　　{

　　while(1)

　　{

　　temp=0xfe;

　　for(i=0;i<5;i++)

　　{

　　if(P1_7==1)

　　{

　　P0=table1[i];

　　}

　　else

　　{

　　P0=table2[i];

　　}

　　P2=temp;

　　a=temp<<(i+1);

　　b=temp>>(7-i);

　　temp=a|b;

　　for(a=4;a>0;a--)

　　for(b=248;b>0;b--);

　　}

　　}