/*
 * myfirst.c 
 * First C program for 2051 experiment
 * complement P1.7 every 0.5 sec
 * Copyright (C) 1999 Wichit Sirichote
 * compiled with Dunfield Micro-C for 8051 Release 3.2
 */

#include c:\mc\8051io.h  /* include i/o header file */
#include c:\mc\8051reg.h

extern register char cputick; // cputick was incremented every 10ms
register unsigned char sec100,flag1;

#define n 50

task1();  // functions declarations
task2();

main()
{
          flag1 = 0;
          sec100 = 0;
          serinit(9600); // set timer0 to be 16 bit counter 
          while(1){

               while(cputick == 0)
                ;
                cputick = 0;
                task1();
                task2();   
                  }
}

task1()                        // set bit 0 of flag1 every n*10ms
{
          sec100++;            // increment sec100
          if (sec100 >= n)
               {sec100 = 0;    // clear sec100
                flag1 |= 0x01; // set bit 0 of flag1
                }
}

task2()
{
         if ((flag1 & 0x01) != 0) // execute below if bit 0 of flag1 is set
                {
                // P1 ^= 0x80;    // exclusive or the latch bit 7 with 0x80
                 asm " CPL P1.7"; // complement P1.7
                 flag1 &= ~0x01;  // clear bit 0 of flag1
                }
}