想在程序里加一个简单的定时左转不知道加在哪里

#include"reg52.h"
sbit L1=P3^1
sbit L=P3^2;
sbit M=P3^3;
sbit R=P3^4;
sbit R1=P3^5;
sbit A1 = P1^0;
sbit A2 = P1^1;
sbit B1 = P1^2;
sbit B2 = P1^3;
sbit C1 = P1^4;
sbit C2 = P1^5;
sbit D1 = P1^6;
sbit D2 = P1^7;
sbit EN1 = P2^5;
sbit EN2 = P2^6;
sbit EN3 = P2^7;
sbit EN4 = P3^1;
typedef unsigned char u;
u falg;
void delay(unsigned int k)
{
unsigned int x,y;
for(x=0;x<k;x++)
for(y=0;y<2000;y++);
}
void run(void)
{
A1=1;
A2=0;
B1=0;
B2=1;
C1=1;
C2=0;
D1=0;
D2=1;
EN1=1;
EN2=1;
EN3=1;
EN4=1;
}
void backrun(void)
{
A1=0;
A2=1;
B1=1;
B2=0;
C1=0;
C2=1;
D1=1;
D2=0;
EN1=1;
EN2=1;
EN3=1;
EN4=1;
}
void leftrun(void)
{
A1=0;
A2=1;
B1=0;
B2=0;
C1=0;
C2=1;
D1=0;
D2=0;
EN1=1;
EN2=1;
EN3=1;
EN4=1;
}
void rightrun(void)
{

A1=0;
A2=0;
B1=1;
B2=0;
C1=0;
C2=0;
D1=1;
D2=0;
EN1=1;
EN2=1;
EN3=1;
EN4=1;
}
void stopruo(void)
{
A1=0;
A2=0;
B1=0;
B2=0;
C1=0;
C2=0;
D1=0;
D2=0;
EN1=0;
EN2=0;
EN3=0;
EN4=0;
}
void main(void)
{
if(L1==1&&L==1&&M==1&&R==1&&R1==1) falg=0;
run();
delay(100);
while(1)
{
run();
delay(400);
delay(400);
} }

搜索一下C语言怎么用定时器吧