# Help setting the correct fuses in AVR Studio (4)

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#### Marks256

##### New Member
I'm curious as to what all the options are for the external crystal/resonator! There has to be at least 50 different options! I am using a 7.3728MHz external clock. What should i set for the fuse? low freq, medium freq, or high freq? And what does the "start-up time: 1K CK + 4 ms; [CHKSEL...]" mean? I am assuming it is how long it takes to start executing code after power on...

Thanks!

#### dougy83

##### Well-Known Member
Doesn't it say the freq range when you select 1 of the '50' options? I would think 7.8MHz is 'medium' speed. The startup time is the delay before the CPU starts working from oscillator startup. It's to make sure the oscillator is stable before executing code. You can check your datasheet about what everything means.

#### Marks256

##### New Member
Aaah that makes sense! Thanks dougy83.

No it doesn't give freq ranges. I just chose medium, and it works fine.

#### Papabravo

##### Well-Known Member
Contrary to reveald truth, the AVR designers did not put those options in just to confuse and annoy you. They did it because there is an incredible range of devices that can be used to generate a clock, including oscillators, crystals, resonators, and passive components. The data sheet will specify a maximum frequency according to the detailed part number. That maximum frequency may depend on Vcc range and other things. If pressed I would say as a rule of thumb, in the absence of better information:
Code:
low ≡ fosc < 25% max
high≡ fosc > 75% max
medium is everything else
On thing I have noticed is that the parts really want to try and work, even when the programmer (you and me) makes occasional mistakes.

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#### johnsmith123

##### Member
here is a link to a fuse calculator online:
Engbedded AVR Fuse Calculator

if you use avrdude (provided your programmer works with avrdude)
the above URL will output the exact string to cut & paste in the avrdude.bat file.

I saw this programmer here:
**broken link removed**
to repair your avr if you mess up your fuses.

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#### shom_show

##### New Member
Myself Sumanta is trying to implement a logic of Blinking LED's with AVR STUDIO4 and Microcontroller ATMEGA32. I am trying to implement with 1 seconds of turn on and

turn off of the LEDs. Although while debugging it shows that the LED on a particular pin of a particular port is blinking with 1 seconds duration. In practical Bredboard, it is

found that the LED remaining ON constantly. Please suggest me what went wrong with the program or any other settings. .

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