AVR Freaks

Hello,

I`ve bought a brand new Board . This has a 7.3728Mhz Crystal and a Atmega128A Core.

Code blinking a LED on PA0:

#define F_CPU 73728000UL
#include <avr/io.h>
#include <util/delay.h>

int main(void)
{
DDRA=0xFF;
while(1)
{
	// cyle 2,168s:
	_delay_ms(50);
	PORTA=0x01;
	_delay_ms(50);
	PORTA=0;
}
	return(0);
}

This works, but the period is 2,168s. Too slow. Must be 0,1s (see Appendix from scope)

In Projekt > properties > device I see no Speed assiged:

Now Tools > Device progamming > fuses

How can I program the correct Speed?

I found a tip in the datasheet page 37:

Default Clock

Source

The device is shipped with CKSEL = “0001” and SUT = “10”. The default clock source setting is

therefore the Internal RC Oscillator with longest startup time. This default setting ensures that all

users can make their desired clock source setting using an In-System or Parallel Programmer.

I am afraid that I will make the chip useless

What should I do?

friendly regards

Ellen