Re: C64 IEEE interface

From: Michał Pleban <>
Date: Wed, 05 Nov 2014 21:15:21 +0100
Message-ID: <>
Hello! wrote:

> On possebility is to reserve a byte and using the bits to tell what 
> device is or isn't IEEE. Another possebility, first check if a IEEE 
> device is present and when not, assume it is IEC.
> Any ideas or comments are welcome!

As I recall (this was some years ago...) my CBM-II IEC cartridge does
the equivalent of combining these two together. That is, I have a byte
with a flag telling if the device is IEC or IEEE. This works a follows:

* If flag not set, call IEEE first. If timeout, call IEC. If IEC found,
set flag.
* If flag set, call IEC first. If timeout, call IEEE. If IEEE found,
clear flag.

So basically the flag tells on which bus the device was last seen, so
that you know where to look first on the next access, without
unnecessary delays, timeouts etc. On the other and, this will still work
when you disconnect the device and connect another one on another bus.

There is also another flag, meant to force a device on specific bus, not
sure whether this is very useful but I added that because it was easy to
do ;-)


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Received on 2014-11-05 21:00:07

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