/*************************************************************
*       at85-0.c - Demonstrate simple I/O functions of ATtiny85
*
*       Program loops turning PB4 on and off as fast as possible.
*
* The program should generate code in the loop consisting of
*   LOOP:   SBI  PORTB,4        (2 cycles)
*           CBI  PORTB,4        (2 cycles)
*           RJMP LOOP           (2 cycles)
*
* PB4 will be low for 4 / clock freq
* PB4 will be high for 2 / clock freq
* An internal 8MHz clock with CLKDIV8 enabled gives a loop period
* of about 6 microseconds.
*
* Revision History
* Date     Author      Description
* 11/02/12 A. Weber    Initial Release
*************************************************************/

#include <avr/io.h>

int main(void)
{
    DDRB |= 1 << DDB4;          // Set PORTB bit 4 for output

    while (1) {
	PORTB |= 1 << PB4;      // Set PB4 to a 1
	PORTB &= ~(1 << PB4);   // Set PB4 to a 0
    }

    return 0;   /* never reached */
}