On Tue, 10 Apr 2001, Ruud Baltissen wrote: > About compatibility: I don't know any valid reason why a good programmer > would prefer the mirror addresses to program the VIC-II. So I presume all > well written software should run on such an altered C=. A programming error could cause the mirror areas to be written. The control registers for the internal RAM expansion in my C128 (sitting at $d700-$d7ff) interferes with some C64 software, probably because they are trying to write to color RAM ($d800-$dbff) but there is an index overflow. Therefore it is a good thing to have some way to disable the control register. In that expansion, I implemented it by connecting an IRQ output of the 6821 PIA to one of its active-high CS inputs. I don't remember if I had to wire something extra to make sure that interrupts can be triggered on the chip by software. Marko - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tml.hut.fi.
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