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Re: [avr-chat] Trouble with USART0 on ATmega644A

From: Rick Mann
Subject: Re: [avr-chat] Trouble with USART0 on ATmega644A
Date: Thu, 6 Jan 2011 19:46:01 -0800

On Jan 6, 2011, at 18:20:06, David A. Lyons wrote:

> 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.

Yep, I'm quite familiar with "programmed" meaning 0. But that is not the same 
as saying that "programmed/0" means "this feature enabled." Does it? I'm never 
sure. A "1" usually means a feature is enabled (otherwise things are 
active-low, and have a bar over them ;-) ).


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