Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!linus!decvax!harpo!ihnp4!inuxc!pur-ee!uiucdcs!miller
From: miller@uiucdcs.UUCP (miller )
Newsgroups: net.micro
Subject: new io ports for the c64 - (nf)
Message-ID: <4842@uiucdcs.UUCP>
Date: Tue, 10-Jan-84 22:26:13 EST
Article-I.D.: uiucdcs.4842
Posted: Tue Jan 10 22:26:13 1984
Date-Received: Sun, 15-Jan-84 01:00:37 EST
Lines: 19

#N:uiucdcs:10400097:000:838
uiucdcs!miller    Jan 10 16:55:00 1984


I also posted this question to net.micro.cbm.  Sorry to all you non-Commodore
users out there; this is the first duplicate posting I've ever done, but I'm
desperate for an answer and I thought this might get a larger readership.


I am trying to add new I/O ports onto my c64 through the expansion port.  I
want them to look like the user port, only in a different address space.  I
tried duplicating the hardware (pull up resistors, etc.) and control lines
used in CIA 2 out the back of the expansion port.  But for the chip select,
I used I/O1 or I/O2 instead of CIA2 (which should map into $DF00 or $DE00).
Unfortunately, this did not work.  I get the handshaking line out the back of
the 6526 to flip, but the output data lines stay high.  Has anyone ever added
extra I/O ports onto the c64 and can offer suggestions?

A. Ray Miller