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Newsgroups: comp.sys.sinclair
From: Andrew Owen <ao...@brandnewco.org>
Date: 2000/05/18
Subject: Re: RFC: ULA Replacement for ZX Spectrum SE
in article ye8ln18jd5c....@cass52.hoyle.star.fleet, Philip Kendall at
p...@ast.cam.ac.uk wrote on 18/5/00 12:44 pm: > I think you need to start thinking in terms of bit fields, rather than Acording to Pera's info bit 4, 2 and 3 are free. If IF1 uses 2 and 3 then > simple numbers. The problem here, is that all the low 8 bits are taken > by something (ULA, 128Kb/Sinclair joysticks, disk interfaces, > Interface 1 x 2, Kempston x 3). To work out what's free, we're going > to have to find out the decoding schemes used by all these > interfaces... that leaves bit 4. I would have used the ULA's port but that also handles the sound and load/save so that's not an option. This would make port 88h a possible contender yes? What stuff uses bit 4 at > OTOH, if we're not going to be writing large amounts of data to this It's not a lot of info but how do we do this without disturbing the lower > port, we could consider using one of the upper 8 bits of the bus, as > the extra set up time wouldn't then be important. part? > If we do want to use a port under #100, we may have to go for an Ugly I don't know! :( > Hack solution of making it use either bit 2 or 3, and just say > `Sorry. You can't use this if you've got both a disk interface and an > If1 attached' -- what compatability problems are there between the > various disk interfaces and the If1 at present? For example, can you > use an MB02 with the If1? -Andrew You must Sign in before you can post messages.
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