速来！单片机题，有没有会的

Question

假设系统的晶振频率为12MHz，使用定时器T0采用方式1定时，在P1.0端口输出频率为1HZ，占空比为2:5的矩形脉冲。

Answer 1

#include "reg51.h"

unsigned char BYTE;
unsigned int WORD;

//-----------------------------------------------

/* define constants */
#define FOSC 11059200L

#define T1MS (65536-FOSC/12/1000) //1ms timer calculation method in 12T mode

/* define SFR */
sbit TEST_LED = P1^0; //work LED, flash once per second

/* define variables */
unsigned int count,count_h=0; //1000 times counter

//-----------------------------------------------

/* Timer0 interrupt routine /
void tm0_isr() interrupt 1
{
unsigned int j=500;
TL0 = T1MS; //reload timer0 low byte
TH0 = T1MS >> 8; //reload timer0 high byte
j=10002/7;
if(count_h<j) /////占空比值
count_h++;
else
TEST_LED=0;
if (count-- == 0) //1ms * 1000 -> 1s
{
count = 1000; //reset counter
count_h=0;
TEST_LED =1; //work LED flash
}
}

//-----------------------------------------------

/* main program */
void main()
{
TMOD = 0x01; //set timer0 as mode1 (16-bit)
TL0 = T1MS; //initial timer0 low byte
TH0 = T1MS >> 8; //initial timer0 high byte
TR0 = 1; //timer0 start running
ET0 = 1; //enable timer0 interrupt
EA = 1; //open global interrupt switch
count =1000; //initial counter
count_h=0;
TEST_LED =1;
while (1); //loop
}