Re: I/O Expander

From: Andre Fachat (a.fachat_at_physik.tu-chemnitz.de)
Date: 1998-01-05 12:34:27

MagerValp wrote:
> 
> Hello everyone.
>   I spent most of christmas day soldering in my C64 and since the
> result was quite useful I thought I'd share it with the world. My I/O
> expander divides the D000-D7FF area into eight chunks instead of the
> normal two giving you plenty of space for hardware expansions. I
> uploaded the project schematics to the CBM archive at funet last
> night, and should appear there shortly. You can find it on my homepage
> as well, at
> 
>   http://www.cling.gu.se/~cl3polof/IO/
> 
Isn't there a bug in the pin description of the 74ls138?
Shouldn't it be /E1, /E2 and E3?
Then the logis also is ok, because the NAND (74ls00) output
is low when inactive and high when active.

The schematics itself (besides this) seems to be correct. 
Nevertheless one has to handle the Phi2 delay issue when
connecting a 6522 -- but any CBM hacker should know that already... :-)

so long
Andre

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Andre Fachat, Institute of physics, Technische Universitšt Chemnitz, FRG
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