[Coco] 6502 to 6809 translation
Phill Harvey-Smith
afra at aurigae.demon.co.uk
Mon Aug 1 07:02:13 EDT 2011
Hi All,
I'm currently trying to translate some 6502 code to run on the
Dragon/CoCo, all is prety easy except for one thing, the 6809 doesn't
appear to have one of the 6502 indexed modes namely :
asume that data_addr contains $8000
and y=$20
lda (data_addr),y
which will IIRC take look in data_addr, find $8000 and load a from
$800+$20 = $8020.
the 6809 has
lda (data_addr,y)
but this will load a from where data_addr+$20 points to, which is not
the same thing !
So is there an easy way of translating the 6502 code in a couple of 6809
instructions ?
Cheers.
Phill.
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