Re: Got IEC code working

From: Marko Mäkelä (
Date: 2004-05-26 09:02:29

On Tue, May 25, 2004 at 04:50:08PM -0500, Jim Brain wrote:
> I came up with this, but it's just a stab at something, comments are 
> appreciated:
> (all data in hex)
> FF is "command" char.  If it appears in data stream, replace with FF FE
> FF 00   reset interface
> FF 01 X   listen as device X
> FF 02 X unlisten as device X

I don't think that it is good idea to allow listening for only one device
number at time.  A file and print server application running behind the
serial line may need to emulate several devices at the same time.  There's
not enough time to notify the application over serial bus requests and wait
for the decision whether the request should be replied.  That's why I
went for a command "listen to these device numbers" that takes 31 bits as
a parameter (actually 32, but device number 31 is ignored).

> I have some other higher level commands, but wondered what folks thought 
> of these.  I tried to decipher Marko's format, but I can;t figure it out...

My format should be adequate for all uses, expect defining custom fastloader
protocols.  Maybe it would help if you constructed the transition diagram for
the serial bus and had a look at the serial bus routines in the Vic-20
and 1541.  I can't find the PNG file I made from my diagram, but I have the
piece of paper somewhere.  Anyway, it would be a good idea to produce it
independently.  I used three kinds of transitions: timeouts, inputs (waiting
for state transition) and outputs (changing the state of a line).


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