Re: [avr-gcc-list] swap bits

[Kang Tin LAI]

May reduce the hardware port pin by using 4-bit nibble connection:
PA0 - PA7
PA1 - PA6
PA2 - PA5
PA3 - PA4
with few additional instructions to combine nibbles back to byte.

--
---
Kang Tin LAI <address@hidden>
-----

Klaus Rudolph wrote:

> Volkmar Dierkes wrote:
> I have another, but not really a good idea...perhaps :-)
>
>
> > What do you mean with efficiently? bytes or time?
> or IO-Pins?
>
>
> Make port A output and port B input. Make a wirering
> port A[0]->portB[7] ....
> You need only two bytes flash for program + initialisation 
> and waste no registers :-)
>
> init:   ldi r16, 0xff
>         out ddra, r16
>
> reverse_r16:
>         out porta, r16
>         in r16, portb
>
> 4 words flash, and 4 cycles access time.
> Thats really effectiv!
>
> Bye
>         Klaus
> avr-gcc-list at http://avr1.org



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