Question

单片机：80C51的中断系统及定时/计数器

要求从P1.1引脚输出1000Hz方波，晶振频率为12MHz。试设计程序。

Answer 1

org 0000h
ljmp reset
org 000bh
ljmp int_time
ORG 0030H
RESET: mov sp,#07h
mov r0,#7fh
clear0: mov @r0,a
djnz r0,clear0
MOV TMOD,#01H ;设定定时器0
MOV TL0,#0cH ;设定定时初值65536-500
MOV TH0,#0FeH
setb ea
setb ET0
setb tr0
ajmp $

int_time:
mov tl0,#0ch
mov th0,#0feh
cpl p1.1
reti

end

Answer 2

#include <reg51.h>
sbit OUT = P1^1;
void InitTimer0(void)//1ms定时中断初始化
{
TMOD = 0x01;
TH0 = 0x0FC;
TL0 = 0x18;
EA = 1;
ET0 = 1;
TR0 = 1;
}
void main(void)
{
InitTimer0();
while(1);
}
void Timer0Interrupt(void) interrupt 1 //1ms定时中断
{
TH0 = 0x0FC;
TL0 = 0x18;
OUT = ~OUT;
}