Embedded Systems Design with the Atmel AVR Microcontroller Part II

}
}
case 0x02: //CCW
while((PINB & 0x03)==0x02)
{
PORTD = 0x10;
delay(15);
PORTD = 0x00;
delay(1);
PORTD = 0x20;
delay(15);
PORTD = 0x00;
delay(1);
PORTD = 0x40;
delay(15);
PORTD = 0x00;
delay(1);
PORTD = 0x80;
delay(15);
PORTD = 0x00;
delay(1);
break;
7.6. DC MOTOR SPEED AND DIRECTION CONTROL 227
default:; //all other cases
} //end switch(new_PORTB)
} //end if new_PORTB
old_PORTB=new_PORTB; //update PORTB
//*************************************************************************
//int_timer0_ovf_interrupt(): The Timer0 overflow interrupt is being
//employed as a time base for a master timer for this project. The internal
//oscillator of 8 MHz is divided internally by 8 to provide a 1 MHz time base
//and is divided by 256. The 8-bit Timer0
register (TCNT0) overflows every
//256 counts or every 65.5 ms.
//*************************************************************************