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Re: [avr-gcc-list] Glitch on GPIO

From: Galen Seitz
Subject: Re: [avr-gcc-list] Glitch on GPIO
Date: Fri, 24 Feb 2006 07:08:09 -0800

Jahagirdar Gopal-AGJ005 <address@hidden> wrote:

> HI,
> I have one peculiar problem here. 
> One of the GPIO of atmega128, has been pulled up. When atmega128 boots
> up, initialization script makes that GPIO pin high, irrespective of what
> is pulled up (Atmega does not start booting immediately the power is
> given. There is some delay given purposely between power-up and
> execution de-assertion of reset signal). So the expected behavior is
> that pin should continue to be high as measured on CRO. But there is a
> glitch (10us) on that pin when GPIO is written high by software. 
> Any idea on this behavior? Can this be solved?

Are you writing to the direction register before writing to the data
register by any chance?  It would be helpful to see the initialization 


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