Re: Help with SX64 User Port?

From: Gerrit Heitsch <>
Date: Tue, 13 Oct 2015 07:48:23 +0200
Message-ID: <>
On 10/13/2015 03:09 AM, Leif Bloomquist wrote:
> Hi all,
> Some of you know I've been tinkering with an Arduino-based Wifi
> "Modem" for the Commodore 64 etc.  (Pics here:
> It's almost ready to go, however, one issue is that it doesn't work on
> the SX64, and it's the same issue on at least two SX's.
> The symptom is that while the Arduino receives serial data from the SX
> fine, nothing sent by the Arduino is received by the SX.   I've also
> tried going directly to the Wifi board (which is also serial), same
> issue.   It works fine on a normal 64/64C though.

What kind of CIAs do the different Systems use? At the end of 1986, 
Commodore changed the process from NMOS to HMOS-II. For a short while, 
some CIAs were labeled '8521R0' but then they went back to the '6526' 
label. Usually they were also fast enough for get the 'A' for 2 MHz 
operation. The HMOS-II-CIA also changed a bit timingwise, that's where 
the legend originated that the 6526A behaves differently than the 6526.

So the question is, does the HMOS-II-CIA work where the NMOS-CIA doesn't?


       Message was sent through the cbm-hackers mailing list
Received on 2015-10-13 06:00:08

Archive generated by hypermail 2.2.0.