Path: utzoo!utgpu!watmath!isishq!f171.n221.z1.FIDONET.ORG!izot
From: izot@f171.n221.z1.FIDONET.ORG (Geoffrey Welsh)
Newsgroups: comp.sys.cbm
Subject: 6551 interfacing
Message-ID: <2384.2474E383@isishq.FIDONET.ORG>
Date: 19 May 89 13:46:29 GMT
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 > From: bowen@cs.Buffalo.EDU (Devon E Bowen)
 > Message-ID: <5944@cs.Buffalo.EDU>
 
 > I've got the chip set up so it takes
 > over the I/O expansion area number 1 from 6E00 to 6EFF by running the
 > chip select directly to the IO1 pin on the bus.
 
   That should put the chip at $DE00, not $6E00.
 
 > It was suggested to me that I might have some contention between chips
 
   If you used IO1 and don't have any other cartridges that also use the IO1 
slot (e.g. C64-Link), then I wouldn't think that's the problem. The IO1 signal 
is only enabled if the correct bank AND address are selected (one of the 
functions of the 82S100 PLA), so you're not going to be in contention with RAM 
or the character generator.
 
   It might be that other chip select lines aren't properly selected (might 
they be floating, or connected to other lines?)...
 
 > The one thought I had was that maybe I have to do something
 > with either the GAME line or the EXROM line. These lines aren't described
 > very well in the book and on the schematics the logic gets lost in the
 > PLA. Anyone know if I need to tug on one of these?
 
   No, leave them floating (or pull them high). You only need these if you're 
going to be imposing ROM in the C64 memory map.
 


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