[Coco] 6502 to 6809 translation

[John Kent]

Rather than using Y you might want to use B,

that way

lda (data_addr),y

would become

ldy data_addr
lda b,y

John.

On 1/08/2011 9:02 PM, Phill Harvey-Smith 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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>


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