Re: [avr-gcc-list] Is it possible to implement...

[E. Weddington]

On 30 Dec 2002 at 21:59, Rune Christensen wrote:

> Hello
> 
> Is it possible to implement the following code in avr-gcc not using
> assembler
> 
> if (carry(csumlo += data))
> {
>   if (carry(++csumhi))
>   {
>     csumlo++;
>   }
> }
> 
> Now it's implemented as
> 
> csumlo += data;
> if (csumlo < data)
> {
>   if (++csumhi==0)
>   {
>     csumlo++;
>   }
> }
> 
> But I want to optimize it with the carry-bit
> 
> Thanks in advance
> 
> Rune Christensen

Well you can access the status register in C by using SREG. SREG is 
defined in the processor IO header files (like iom128.h). The carry 
bit is bit 0 in SREG, so you should be able to implement an algorithm 
using this.

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