/* --- STC12C5Axx Series 16-bit Timer0 Demo -------------------------*/


#include "reg51.h"

typedef unsigned char BYTE;
typedef unsigned int WORD;

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

/* define constants */
#define FOSC 11059200L
#define MODE1T                      //Timer clock mode, comment this line is 12T mode, uncomment is 1T mode

#ifdef MODE1T
#define T1MS (65536-FOSC/1000)      //1ms timer calculation method in 1T mode
#else
#define T1MS (65536-FOSC/12/1000)   //1ms timer calculation method in 12T mode
#endif

/* define SFR */
sfr AUXR = 0x8e;                    //Auxiliary register
sbit TEST_LED = P0^0;               //work LED, flash once per second

/* define variables */
WORD count;                         //1000 times counter

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

/* Timer0 interrupt routine */
void tm0_isr() interrupt 1 using 1
{
    TL0 = T1MS;                     //reload timer0 low byte
    TH0 = T1MS >> 8;                //reload timer0 high byte
    if (count-- == 0)               //1ms * 1000 -> 1s
    {
        count = 1000;               //reset counter
        TEST_LED = ! TEST_LED;      //work LED flash
    }
}

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

/* main program */
void main()
{
#ifdef MODE1T
    AUXR = 0x80;                    //timer0 work in 1T mode
#endif
    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 = 0;                      //initial counter

    while (1);                      //loop
}