Single chip microcomputer dynamic digital display technology

1. Experimental tasks

As shown in Figure 4.13.1, the P0 port of the AT89S51 microcontroller is connected to the font 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

Figure 4.13.1

3. Hardware connection 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 a cycle. When the cycle display frequency is high, the human eye's retention characteristics are used to prevent the flickering display phenomenon from being visible. 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 [page]

5. Flowchart

Figure 4.13.2

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,$

DJNZ R6,D1

RET

TABLE1: DB 06H,5BH,4FH,66H,6DH

TABLE2: DB 78H,79H,38H,38H,3FH

END

[page]

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--);

}

}

}