Subject: Re: [stella] A new way to bankswitch From: "Kroko" <Nil.Krokodil@xxxxxxx> Date: Thu, 10 Mar 2005 14:44:30 -0500 |
Hi ! >I wonder if it would work in a 16k scheme We need RTS on all hotspot adresses (except for the last hotspot) in each bank In addition, we need one RTS which is located one adress below the first hotspot. I think that doesn't matter too much, because it is difficult to use this ROM space for other things anyway. F8: FFF7: RTS FFF8: RTS FFF9: ... F6: FFF5: RTS FFF6: RTS FFF7: RTS FFF8: RTS FFF9: ... F4: FFF3 RTS FFF4 RTS FFF5 RTS FFF6 RTS FFF7 RTS FFF8 RTS FFF9 RTS FFFA RTS FFFB ... No matter in which bank we are, if we have RTS in these adresses in every bank, we can switch banks by 1. push target adress to stack And then for F8: jump to $(FFF7+TargetBankNr) F6: jump to $(FFF5+TargetBankNr) F4: jump to $(FFF3+TargetBankNr) When the adress of the jump target is on the bus, we first switch to a wrong bank, which does not matter as long as the processor finds an RTS there. The following dummy fetch will then bring us to the right bank and the execution of the RTS brings us to the correct location in that bank. So yes, I think it should be usable also for F6,F4 and even EF ... I did not test it, but I think it could work :-) Armin Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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