Are A14 and A15 necessary with this little amount of memory? Am 6. August 2016 18:37:41 schrieb Segher Boessenkool <segher@kernel.crashing.org>: > On Sat, Aug 06, 2016 at 06:13:40PM +0200, Michał Pleban wrote: >> > Right, that makes sense... Except SID is treated "properly"! >> >> Yes, that's true. But maybe it's because they wanted to make SID write-only? > > No, the paddle regs need reading, and the counters do (wave form, > envelope of chan 3). The MAX has the paddles wired up (with a 4066 > no less) so it is meant to be used :-) > >> It's hard to explain it. When I hook up the GAL instead of 6703, we can >> try to see if "fixing" the equations makes any difference - maybe >> there's some reason to them, or maybe not. >> >> >> Maybe that's not very relevant, since the VIC memory map seems to >> >> repeat itself every 16 kB. >> > But not the 6703 equations! >> >> They do with regard to RAM and ROM. The IO chips are an anomaly, but >> they don't overlap with RAM and ROM in the VIC memory map. So maybe >> nobody bothered to fix the equations for them. > > Yeah. > >> It would be interesting to write some software which tries different >> settings of VIC registers to see if it really "sees" these chips. Plus I >> still don't know what drives the A15..A14 lines on VIC access - are they >> just left floating? > > Probably. There are two schematics of the MAX in circulation, both > different, and both wrong it seems. Or they are for different generations > hardware. But neither has this dealt with afaics. > > If nothing drives an address line it will hold its value for a value, > and eventually drop to 0. There is nothing that would pull the line > one way or the other as far as I can see. > > > Segher > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2016-08-06 18:00:02
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