Hallo Marko, > My question for PET experts is: Are there free I/O block selection signals > on the expansion port? The VIA's, CRT and PIA resides on $E8xx. The only lines available are those covering $4xxx until $Bxxx in steps of $1000. I had a quick look at the various docs of Olaf but couldn't find anything that said that $E900-$EFFF is used by ROM or whatever. $9xxx and $Axxx are free for onboard ROM-expansion. So IMHO you have two solutions: - you use $9xxx and/or $Axxx - you use $E9xx..$EFFF (if available), but complete decoding needed > And regarding the 6545 CRTC: are the registers R18 > through R31 unassigned? Seen from the CPU, the 6545 only uses two registers. So the fact that the INTERNAL registeres R18/31 are used or not, doesn't matter. Groetjes, Ruud http://Ruud.C64.org - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tml.hut.fi.
Archive generated by hypermail 2.1.1.