Re: [stella] Supercharger Bankswitches and RAM access!

Subject: Re: [stella] Supercharger Bankswitches and RAM access!
From: Chrissalo@xxxxxxx
Date: Sat, 15 Mar 1997 20:12:08 -0500 (EST)
<< So, you know how loading works? Can you explain to me, what a game has to
do to load another part, please?
Ciao, Eckhard Stolberg

oh my, there I did something ;-)

I don't know exactly, I just implemented what I found on the 
'Stella gets a new brain' CD...

(I hope nobody does REWIND anything, 'cause I didn't do that yet..., don't
  where the ROM exits to either...)

  . . . . . POWER UP ROM
  . . . . . WAIT > 1000 CYCLES
  . . . . . $80 - D7-D5 ONE SHOT (leave location $80, bits 5-7 intact!)
  . . . . . $FA - SEQUENCE BYTE  (multiload number to load next in location
  . . . . . STACK POINTER > $FD

  . . . . . JMP $F800

Well, from what I gather from the above:
Switch to a bank switch mode which enables the ROM (0,1,4,5)
load the values you need to  $80 (bankswitch scheme RAM/options...)
The sequence number to $FA
(dunno about the sequence number, one should think they are sequential,
but for dragonstomper e.g. they are 0,4,5).
Than (or before) you have to wait for those 1000 cycles.
(well for the emu it is not neccessary)
Than do the above mentioned $f800 jump.
What I do after loading, is jumping to location that is allocated
at $2000-$2001 in the header of the tape images, which is supposed to be
the starting vector. Works great so far!

hope that helped, but probably didn't ;-(


I didn't realize before, that indirect addresses were only possible via zero

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