How to run ATTINY45 at 20Mz??

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Hello,

reading datasheet seem that this micro is able to run at 20MHz but in fuse bit there isn't this voice.

What I can do?
Use External cristal on PB3 and PB4?

If this is the case, which fuse bit I should use?

Thanks

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See page 30 etc. of the data sheet.

Leon Heller G1HSM

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I have already see it but not talk about 20Mhz and wich kind of fuse setting in this case.
In my case I don't need frequency stability at start up
Thanks

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You'll need an external crystal or oscillatot. Then choose the fuse setting to select this.

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Quote:

reading datasheet seem that this micro is able to run at 20MHz but in fuse bit there isn't this voice.

What does the last entry in table 6-12 say? Combine this with the last entry in table 6-13

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Pratically the last option in AVR STUDIO 4 fuse bit setting. Correct?

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Quote:

Pratically the last option in AVR STUDIO 4 fuse bit setting. Correct?


Yup, correct.

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You can get ~16MHz by ramping osccal up to 255. Setting it above 8.8MHz breaks writing to flash and eeprom. Search datasheet for OSCCAL.

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dak664 wrote:
You can get ~16MHz by ramping osccal up to 255. Setting it above 8.8MHz breaks writing to flash and eeprom. Search datasheet for OSCCAL.

It is a trick for run internal oscillator almost at 16Mhz without Quartz?

Not is Instable in this manner?

If not how you change OSCCAL?

Thanks

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What the heck are you guys talking about? The Tiny25/45/85 has an internal 8x PLL which can also be used as a 16 MHz system clock. Along with a properly tuned OSCCAL value, the 20 MHz system clock can be easily generated.

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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just curious, are there attinys that have internal clocks accurate enough to do USART like the xmegas? I know their implementation is different.

I ask because these attinys have small pin counts and it would be silly devoting pins to external crystals.

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You can manually calibrate the OSCCAL within +-0.25% at a room temperature and a fixed, regulated supply voltage, and get it stable within +-2% over the -40..+85C temperature range. This is at least twice over the allowed error limit for asynchronous communications, albeit in a limited temperature range (e.g. 20 +-10C) it might be feasible.

Warning: Grumpy Old Chuff. Reading this post may severely damage your mental health.

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Quote:

I ask because these attinys have small pin counts and it would be silly devoting pins to external crystals.

Would it be so silly if making an industrial timer?

Anyway, how many Tinys have hardware USARTs? USI doesn't count (IMO). Tiny2313 family doesn't count either--Mega48 is smaller, about the same price, and has real microcontroller features such as A/D. You gonna do software UART? Full duplex, and dedicate all of your timers?

Fuggedaboudit; start with Mega48 family unless a true "tiny" app.

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

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choose

Ext. Crystal 8.0- MHz in drop down list of STK