Re: [Tuxnes-devel] yet more asm stuff--carry f

[Jim U. <ji...@3e...>]

At 12:02pm on 2001 April 17, Rigel did write:
> >> let's say the operation is sh left, so in C:
> >> modified=orig<<1;
> >> carryf = modified ^ orig; // ^ is xor operator (?)
> 
> >Um... try, for example, orig=1.  This gives carryf = 3.
> >xoring won't work except by chance. ;)
> 
> >For ASL, try something like
> >carryf = (orig & 0x80) ? 1 : 0;      
> >or equivalently
> >carryf = (orig & 0x80) >> 7;
>       
> >Grab a copy of an (unencumbered) C 6502 core (e.g. Nofrendo) because
> >it will tell you exactly how every instruction works in a high-level
> >language.
 
> I thought anything non-zero was true (even in asm)?  I was working under that assumption, (assuming makes an ass out of "u" and "me"...).
But ASL when A=01 does not carry.

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