51 MCU 1 second timing C language program (through debugging)

#include
#include
#include

   /***************************
* Define hardware pin connections
****************************/
sbit p1_0=P1^0;             
 /*****************************
* Define global variables
***********************/
// Byte data intrCounter; // Number of timer interrupts
// Byte data beginNum; // Time to start countdown
 //Byte data counterBack; // Store the number of interrupts in it for later use
unsigned char intrCounter;
unsigned char beginNum; 
unsigned char counterBack;
void IT0_Init(void);
void Timer0_Overflow();
void GetCounter(void);
void main()
{
 p1_0=1;
 GetCounter() ;Change once every second;
 p1_0=!p1_0;;
}
/*********************************
* GetCounter
*
* Description: Get the preset countdown time
*******************************/
void GetCounter(void)
{
//beginNum=1;//When all switches are not turned, the countdown is 1 second, which is better than setting it to 0 seconds
intrCounter=20;//The number of interrupts corresponding to each second is 20 times
}
/********************************
* IT0_Init
* Description: Initialize the status of timer T0
********************************/
void IT0_Init(void)
{
TMOD=0x01;//Set T0 to work in mode 1
TH0=0x3C;
TL0=0xAF;//These two registers store the starting value of the counter. It is found that the sum of these two values ​​is exactly 50ms after overflow
ET0=1;//Enable T0 interrupt to overflow
EA=1;//Enable total interrupt
TF0=0;//Clear overflow bit
TR0=1;//Enable T0
}

/******************************
* Timer0_Overflow() interrupt 1
* Description: Interrupt overflow service routine, using interrupt mode 1, it is best not to add "using" to select the register group to avoid conflicts with the registers used by the system in the main program

*********************************/
void Timer0_Overflow() interrupt 1
{
static unsigned char second=20;//Use 20 interrupts to determine 1 second
TH0=0x3C;
TL0=0xAF;
second--;
intrCounter--;

if (second==0) //Operation every second
{
   
    second=20; //Reassign the counter per second
   }
   if (intrCounter==0)
   {
    TR0=0; //Close T0 counter
   }