void main ()
{
     unsigned char step_seq;
     unsigned char direction;
     unsigned char i;
     TRISB=0b00000000;// all PORTB will be output and b4 b5 b6 b7 will drive the motor
     TRISA=0b11111111;         // PORTA will be the input signal A0=step   A1=direction
     PORTB=0b00010000; // intial state
     step_seq = 0;
  

     pulse_detect :
                do {} while (PORTA.RA0== 0);          /* loop while Step signal is LO i.e. A0=0*/
                /* Step signal has gone to 1 */
                direction = PORTA.RA1;                 /* get Direction signal input*/
                if (PORTA.RA0 == 0) goto pulse_detect; /* too narrow must be noise reject*/
                i = PORTA.RA1;                         /* read A3 again and temporarily store Direction in i*/
                if (direction != i) goto pulse_detect ; /* compare two samples of Direction reject if not the same */
                do { } while (PORTA.RA0 == 1); /* waite for negative edge of Step signal*/
                if (PORTA.RA0 ==1) goto pulse_detect ;
                if (direction ==0)
                {
                   step_seq++; if (step_seq == 4) step_seq = 0;
                }
                else
                {
                    if (step_seq == 0) step_seq = 4; step_seq--;
                }
                switch (step_seq)
                {
                       case 0: PORTB = 0b00010000;
                       break;
                       case 1: PORTB = 0b00100000;
                       break;
                       case 2: PORTB = 0b01000000;
                       break;
                       case 3: PORTB = 0b10000000;
                       break;
                       default : step_seq = 0;
                }
                 goto pulse_detect; 
  }