Re: I/O Expander

From: MagerValp (MagerValp_at_Goth.Org)
Date: 1998-01-05 13:26:20

>>>>> "Andre" == Andre Fachat <> writes:

MV> Hello everyone. I spent most of christmas day soldering in my C64
MV> and since the result was quite useful I thought I'd share it with
MV> the world. My I/O expander divides the D000-D7FF area into eight
MV> chunks instead of the normal two giving you plenty of space for
MV> hardware expansions. I uploaded the project schematics to the CBM
MV> archive at funet last night, and should appear there shortly. You
MV> can find it on my homepage as well, at


Andre> Isn't there a bug in the pin description of the 74ls138?
Andre> Shouldn't it be /E1, /E2 and E3?

Absolutely correct. I fixed the schematic on the web page, and I'll
update the archives asap.

Andre> Then the logis also is ok, because the NAND (74ls00) output is
Andre> low when inactive and high when active.

Andre> The schematics itself (besides this) seems to be correct.

Well, it works in my machine... :)

Andre> Nevertheless one has to handle the Phi2 delay issue when
Andre> connecting a 6522 -- but any CBM hacker should know that
Andre> already... :-)

Shame on me for not knowing... :) What's the phi2 delay issue?

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