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Re: [avr-chat] Trouble with USART0 on ATmega644A
From: |
David A. Lyons |
Subject: |
Re: [avr-chat] Trouble with USART0 on ATmega644A |
Date: |
Thu, 6 Jan 2011 18:20:06 -0800 |
On Jan 6, 2011, at 5:49 PM, Rick Mann wrote:
>> Besides defaulting to 8MHz, the factory default 'divide by 8' is set, so
>> unless you set the fuses, the part is running at 1MHz.
>
> I think the docs say it's cleared by default. Anyway, I tried both. So, I'm
> very puzzled that Fosc seems to be 1 MHz.
In <http://www.atmel.com:80/dyn/resources/prod_documents/doc8272.pdf>, I see
section 8.2.1, "Default Clock Source" saying:
"The device is shipped with internal RC oscillator at 8.0MHz and with
the fuse CKDIV8 programmed, resulting in 1.0MHz system clock."
To avoid being misled by fuse documentation elsewhere in the docs, always
remember that a "programmed" fuse is 0, and an "unprogrammed" fuse is 1.
Cheers,
--Dave