Re: Direct Page & Stack Page in Bank $00?

[Exegete <millers@noneofyourbusiness.com>]

Bryan Parkoff wrote:

>     I find an interesting issue that 65816 can only restrict Direct Page and
> Stack Page to Bank $00.  I wonder why Western Design Center designed 65816
> to use Bank $00 only.  I would want Direct Page and Stack Page to be in Bank
> $01 through $FF by changing Bank Program Counter Register, but leaving
> Direct Register and Stack Register alone.  Direct Register allows to move
> from Page $00 to between Page $01 and Page $FF.  Stack Register does the
> same like Direct Register does.
>     It is very painful for Western Design Center to tell us that we must use
> Long Address to load and store data in any banks.  

No pain, no gain.

It may be terrible
> design, but is it the way how 65816 is designed?
>     My example code below.
>
> LDA $4000
> STA 00
> PHB
> LDA #01
> PHA
> PLB
> LDA $4000
> STA 01
> PLB
> RTS
>
>     Data must be stored in Direct Page in Bank $00.  I replace from Direct
> Page to Absolute Page.  Take a look below.
>
> LDA $4000
> STA $0000
> PHB
> LDA #01
> PHA
> PLB
> LDA $4000
> STA $0000
> PLB
> RTS
>
>     Data shows in $0000 in both Bank $00 and Bank $01.  It is why I use
> Absolute Page instead of Direct Page.  I really want to use Direct Page in
> both Bank $00 and Bank $01 because I would like to store data pointer there
> however I hate to see that it is always located in Bank $00.
>     What happen if Direct Page has taken 256 bytes?  I tell Direct Register
> to move from Page Zero to Page One and so.  It would be impossible for
> Direct Pointer to contain 512 bytes or 1024 bytes.
>     CPU 6502 and CPU 65C02 allow separate Bank $00 and Bank $01 so Bank $00
> has its own Direct Page and Stack Page while Bank $01 has its own Direct
> Page and Stack Page unlike CPU 65816 does.  

No, they don't. They don't have banks at all. Only the 65816 has banks. 
Now, the Apple II DOES have it's Aux bank, but that is a feature of the 
Apple II, not the 6502.

Please advise...
>



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