[Coco] 6502 to 6809 translation

[Arthur Flexser]

Wouldn't lda data_addr,y (without the parentheses) do the equivalent?
Add data_addr to y and load the a register from the address $8020?

Art

On Mon, Aug 1, 2011 at 7:02 AM, Phill Harvey-Smith
<afra at aurigae.demon.co.uk> wrote:
> 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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