6502 stacks grow down, not up.
On Sat, 1 Mar 2003, Kroko wrote:
> I found the following description of RTS on the net
> according to the document, it is the RTS of a 6510
> CPU. But it is different from the decription, that was
> posted here on the list. It would be interesting to find
> out, what the real cycle order is, because this is
> most important ....
>
> can anybody confirm that this is wrong ?
>
> RTS:
> +---------------+------------------+-----------------------+----------+
> | Cycle | Address Bus | Data Bus |Read/Write|
> +---------------+------------------+-----------------------+----------+
> | 1 | PBR,PC | Op Code | R |
> | 2 | PBR,PC+1 | Internal Operation | R |
> | 3 | PBR,PC+1 | Internal Operation | R |
> | 4 | 0,S+1 | New PCL-1 | R |
> | 5 | 0,S+2 | New PCH | R |
> | 6 | 0,S+2 | Internal Operation | R |
> | 1 | PBR,NewPC | New Op Code | R |
> +---------------+------------------+-----------------------+----------+
--
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