Re: [stella] FE Bankswitching

Subject: Re: [stella] FE Bankswitching
From: "Chris Larkin" <clarkin@xxxxxxxxxxxxx>
Date: Sat, 14 Dec 2002 16:50:22 -0800
Here is how FE bankswitching works....

When a JSR or RTS instuction is executed... it causes two consecutive
accesses to the stack $0180 -> $01FF (Usually it's $01FE or $01FF which is
how it got the FE name)... nothing else is supposed to be able to access the
stack twice in a row but those two instructions.

So once you have detected that the stack has been access twice in a row, you
have to read the D5 bit.  If the D5 bit is high (1) then switch to bank one
(or stay in bank 1).... If the D5 bit is low (0) switch to bank 0 (or stay
in bank 0)

It is correct that the sizes.txt file is incorrect for this bankswitch
scheme... it needs to be fixed...

Thanks to Eckhard for helping me with this question :-)


----- Original Message -----
From: "Mickey Mouse" <snafles@xxxxxxxxxxx>
To: <stella@xxxxxxxxxxx>
Sent: Friday, December 13, 2002 6:56 AM
Subject: [stella] FE Bankswitching

> Can someone help me out with FE Bankswitching?  I am
> working on a Cart Emulator and I cant figure out how
> FE works.  The sizes document is wrong according to
> the stella emulator code documentation.  The code
> is written from the processor point of view so it is
> easy, just look at address bit 13.  But the cart cant
> see address 13.  The cart has to know when to switch
> from the bus (contrary to the code documents), the
> bus is all it has.
> Any help would be great!  My star doesnt shine real
> bright, so use little words please.  Explain from
> carts point of view.  Thanks
> Vern
> _________________________________________________________________
> Add photos to your e-mail with MSN 8. Get 2 months FREE*.
> --------------------------------------------------------------------------
> Archives (includes files) at
> Unsub & more at

Archives (includes files) at
Unsub & more at

Current Thread