Simple square wave generating circuit [51 single chip microcomputer and 8253a]

/*8253 Timed square wave generation experiment   instrument 11802  Ma Wei */
#include<reg51.h>
#include<absacc.h>
#define CMD_ADDR XBYTE[0x7FFB]// Address of the command register 
#define TIMER0_ADDR XBYTE[0X7FF8]// Counter 0 Initial value counter 
void main()
{
    
	// The command register is 00110110, The counter 0, First low then high , The way 3, Binary 
	CMD_ADDR=0x36;
	//  Assign a value to the counter from low to high 0
	TIMER0_ADDR=0x52;
	TIMER0_ADDR=0x09;
	while(1); 
}