Re: [avr-gcc-list] efficiency of assigning bits

[Royce & Sharal Pereira]

Hi,

On Fri, 18 Mar 2005 03:43:19 +0530, Jamie Morken <address@hidden> wrote:
> ----- Original Message -----
> From: "E. Weddington" <address@hidden>
> Date: Monday, March 14, 2005 11:38 am
> Subject: Re: [avr-gcc-list] efficiency of assigning bits
>
>
> > To clear bit 0 and set bits 1,2,3 without disturbing the other bits:
> >
> > PORTD = (PORTD & ~(_BV(0))) | (_BV(1)|_BV(2)|_BV(3));
>
> Thanks that is working!
>
> I noticed this in the avr-libc usermanual FAQ:
>
> "http://www.nongnu.org/avr-libc/user-manual/FAQ.html#faq_intpromote";
>
> So would it be a good idea (for saving uC time) to convert that above  
> line to this:
>
> PORTD = (PORTD & (unsigned char)~(_BV(0))) | (unsigned  
> char)_BV(1)|_BV(2)|_BV(3));

Whew! What a long winded way to do things! This takes less time/energy to  
enter:

PORTD &= ~(1 | (1<<1) | (1<<2));

And is quite readable. It also has the same effect as the (unsigned char)  
attribute above.

--Royce.


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