Subject: Re: [stella] A new way to bankswitch From: "Kroko" <Nil.Krokodil@xxxxxxx> Date: Wed, 9 Mar 2005 17:50:38 -0500 |
Hi Fred ! > I thought about that. It does depend on how fast the hardware operates. > There is only one cycle between $FFF8 and $FFF9 accesses. Standard logic > chips should be more than fast enough for this, it's just that the > hardware > I've seen uses a 0.1 uF capacitor to filter out glitches, and this cap may > slow down the switching enough to cause this to not work. I don't agree on that. Look at the timing diagram for an LDA $FFF8: # address R/W description --- ------- --- ------------------------------------------ 1 PC R fetch opcode, increment PC 2 PC R fetch low byte of address, increment PC 3 PC R fetch high byte of address, increment PC 4 address R read from effective address When the LDA $FFF8 is executed, you only have the effective adress on the bus for one processor cycle. So If the bankswitching hardware does not switch, if it sees a valid adress for one cycle, it will simply not work at all :-) And the 0.1 5F Cap is good for about 3005s delay. I think I calculated that a while ago. Don't know the exact value, but it is in that range. It should switch ! Armin Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://stella.biglist.com
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