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- Path: news.tu-chemnitz.de!fachat
- From: fachat@physik.tu-chemnitz.de (Andre Fachat)
- Newsgroups: comp.sys.cbm
- Subject: Re: Adding a 6522 to my c64
- Date: 19 Apr 1996 08:25:54 GMT
- Organization: University of Technology Chemnitz, FRG
- Message-ID: <4l7imi$dte@narses.hrz.tu-chemnitz.de>
- References: <4ktud1$4jh@madeline.INS.CWRU.Edu> <4kvjat$34g@cc.joensuu.fi> <4l2bgk$jpl@narses.hrz.tu-chemnitz.de> <4l72e4$hp5@seagoon.newcastle.edu.au>
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- Bruce R. McFarling (ecbm@cc.newcastle.edu.au) wrote:
- : > normal RAM. But in $DE** of DF** which are the address ranges for
- : > the IO1 and IO2 chip select lines on the expansion port.
- : I was pretty sure Jarno just got the hex address turned around,
- : and meant $DC00 etc. If you get close enough to the processor (that is,
- Well, there's a much simpler way than selecting on CPU port and so.
- I did the same thing when putting a 6551 ACIA on top of the SID, at
- $d600. I put an extra socket under the SID and connected the data,
- address and control lines that were necessary (r/w, Phi2) to the ACIA.
- Through an external connector I got the CPU IRQ line and address bit 9.
- I disconnected the select line from the SID, feeding it through an
- additional demux, giving the first signal to the SID, for $d4** and
- the second one, for $d6**, to the ACIA.
-
- It seems he had done the same, using one of the CIA instead of the SID.
- That's actually an even better idea, as the CIA has more control lines
- already connected (IRQ). The only thing is to feed the original
- select line through an additional address decoder, giving a select for
- only a part ($dc0*) back to the original CIA, and have the rest
- of the address space for own chips. You have to get additional address lines
- from the motherboard, though.
- But no additional glue needed!
-
- Andre
-
-
- --
- Andre Fachat, Tel:++49-371-531-3551|"I do not feel obliged to believe that the
- Stadlerstr 17, 09126 Chemnitz, FRG | same God who has endowed us with sense,
- a.fachat@physik.tu-chemnitz.de | reason, and intellect has intended us to
- http://www.tu-chemnitz.de/~fachat | forego their use" -- Galileo Galilei
-