用STC12C5A60S2写的超声波C程序

#include<12864.h>
#include<INTRINS.h>
sbit M1=P1^0; //发送高电平脉冲
sbit M2=P1^1;
sbit M3=P4^4; //返回信号
sbit M4=P4^5; //返回信号

int a,num;
float b,c;
unsigned char flag;
unsigned char i,ge,shi,bai;
void delay30us(void);
void delay1s(void) ;
void main()
{
    
M1=0;
P1M1=0;
P1M0=0;
P4SW=0xff;
TMOD=0x11;
EA=1;
ET0=1;
while(1)
{ flag=0;M3=1;M4=1;
TH0=(65536-23963)/256;
    TL0=(65536-23963)%256;
M1=1;
delay30us();
M1=0;