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

[Rigel <ri...@an...>]

>> 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"...).





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