Timing counter T0 is used as timing technology

1. Circuit diagram

Figure 4.16.1

2. System board hardware connection

(1. Connect P1.0-P1.3 in the "MCU System" area to L1-L4 in the "Eight-way LED Indicator Module" area with wires.

3. Programming content

(1. Since the interrupt method is used, the interrupt source must have its interrupt entry address. For the timer/counter T0, the interrupt entry address is 000BH, so a long jump instruction is added to the interrupt entry to execute the interrupt service program. The format of writing the assembly source program is as follows:

ORG00H

LJMPSTART

ORG0BH ;Timer/Counter T0 interrupt entry address

LJMP INT_T0

START: NOP ; Main program starts

.

.

INT_T0: PUSH ACC; Timer/Counter T0 interrupt service routine

PUSH PSW

.

.

POP PSW

POP ACC

RETI ;Interrupt service routine returns

END

(2. Timing for 2 seconds, using 16-bit timing of 50ms, a total of 40 times of timing can reach 2 seconds, an interrupt is generated every 50ms, and the 40 times of timing are completed in the interrupt service program. Similarly, for a timing of 0.2 seconds, 4 times are required to reach 0.2 seconds. For the interrupt program, the interrupt must be disconnected in the main program.

(3. Since each 2-second timer expires, L1-L4 flash alternately. Use ID to identify. When ID = 0, L1 flashes; when ID = 1, L2 flashes; when ID = 2, L3 flashes; when ID = 3, L4 flashes

4. Flowchart

T0 interrupt service program block diagram

Main program block diagram

Figure 4.16.2

5. Assembly source program

TCOUNT2S EQU 30H

TCNT02S EQU 31H

ID EQU 32H

ORG 00H

LJMP START

ORG 0BH

LJMP INT_T0

START: MOV TCOUNT2S,#00H

MOV TCNT02S,#00H

MOV ID,#00H

MOV TMOD,#01H

MOV TH0,#(65536-50000) / 256

MOV TL0,#(65536-50000) MOD 256

SETB TR0

SETB ET0

SETB EA

SJMP$

INT_T0: MOV TH0,#(65536-50000) / 256

MOV TL0,#(65536-50000) MOD 256

INC TCOUNT2S

MOV A,TCOUNT2S

CJNE A,#40,NEXT

MOV TCOUNT2S,#00H

INC ID

MOV A,ID

CJNE A,#04H,NEXT

MOV ID,#00H

NEXT: INC TCNT02S

MOV A,TCNT02S

CJNE A,#4,DONE

MOV TCNT02S,#00H

MOV A,ID

CJNE A,#00H,SID1

CPL P1.0

SJMP DONE

SID1: CJNE A,#01H,SID2

CPL P1.1

SJMP DONE

SID2: CJNE A,#02H,SID3

CPL P1.2

SJMP DONE

SID3: CJNE A,#03H,SID4

CPL P1.3

SID4: SJMP DONE

DONE: RETI

END

6. C language source program

#include

unsigned char tcount2s;

unsigned char tcount02s;

unsigned char ID;

void main(void)

{

TMOD=0x01;

TH0=(65536-50000)/256;

TL0=(65536-50000)%6;

TR0=1;

ET0=1;

EA=1;

while(1);

}

void t0(void) interrupt 1 using 0

{

tcount2s++;

if(tcount2s==40)

{

tcount2s=0;

ID++;

if(ID==4)

{

ID=0;

}

}

tcount02s++;

if(tcount02s==4)

{

tcount02s=0;

switch(ID)

{

case 0:

P1_0=~P1_0;

break;

case 1:

P1_1=~P1_1;

break;

case 2:

P1_2=~P1_2;

break;

case 3:

P1_3=~P1_3;

break;

}

}