[A89] Re: more questions (return value)


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[A89] Re: more questions (return value)




ah thanks very much! i didn't really get the encoding method by how it was
diagrammed in the manual

> Look in the instuction listing. Every instruction description has at the
> top a fiels
> "Instruction Format:"
> this contains the bit-format for each instruction.
> There is not like the z80 just one hexcode for each instruction, but it
> is based on bitfields in the opcode.
>
> If you look at the normal move for example it is:
>
> 00<2 bits size><6 bits destination><6 bits source>
>
> source and destination is <3 bits register><3 bits addressing mode>
> then there is tables for each addressing mode..(An)+ is for ecample 011.
> and just a Dn register is 000.
> so
>
> move.l (a7)+,d3   // Same as move.l (sp)+,d0
>
> becomes:
>
> 00 10 000011 011000
>
> which equals
>
> 0x20D8
>
> in hex.
>
> ///Olle
>



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