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Re: [avr-gcc-list] Is this a Bug??????

From: Geoffrey Wossum
Subject: Re: [avr-gcc-list] Is this a Bug??????
Date: Wed, 31 Jul 2002 08:43:58 -0500 (CDT)

> C   code
> _________________________________________
> cbi( PORTB, 0 );    // sos send
>         while( timer_flag == 0 );  //wait for timer
> cbi( PORTB, 1 );    // seakey send

> In the assembley code, the variable 'timer_flag'
> gets put into register r24 and then gets tested
> repetedly.  The value of timer_flag never gets
> reloaded into r24 the program hangs.

You must declare timer_flag as volatile, otherwise the compiler will make 
the optimization you observed.

Geoffrey Wossum
Project AKO - http://ako.sf.net

avr-gcc-list at http://avr1.org

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