Re: userport: C64, Plus4, others?

Hi Ruud,

On Tue, Mar 06, 2012 at 05:13:45PM +0100, Ruud@Baltissen.org wrote:
> Hallo Gábor,
> 
> 
> > I'm thinking on starting to do some hw development. ....
> > ....
> > First of all, since I don't have too much experience, what do
> > you think, is it such a simple task, or am I wrong?
> 
> With all respect, but you didn't state very clearly what you want to
> do with this uC. You are talking about "transfer rate"; between the
> C64 and uC or between the uC and the outside world? The connection

Surely the transfer rate between C64 and the uC this time only. As far as I
can see:


LDA $DD01
STA BUFFER
LDA $DD01
STA BUFFER+1
[...]

With this "unrolled-loop" the maximal transfer rate can be told, for sure,
in a more realistic example some would use some kind of loop anyway. This
was for reading, something similar for the opposite direction.

And as far as I can understand the things, CIA can provide a (with "PC") for
the uC that new data put on (on C64 write), or data is read (so next can be
placed for read by the C64).

> could be as simple as using the existing RS-232, not slow, but less
> effort needed to program things.
> 
> 
> > I prefer user port, because it exists on other machines as well,
> 
> But they are not all the same! And you need a program to run the
> whole thing. Using the expansion connector you can include the
> program on an EPROM.

I know that they are not the same, but at least as far as I can see, there
is common ground; 8 bit data, programmable input/output, and at least on C64
hardware level handshaking, so I can know if new data is read/written by the
CPU (well of course with the expansion connector it's even more trivial as I
can tell when there is R/W for the I/O area, etc).  However the major point,
that DTV does not have an expansion port/connector at all, but it has user
port (though afaik there is no "PC" handshaking line there).

What I would like to build some stupid prototype board, which can be
connected to at least DTV and C64 too (I am not sure about the Plus/4
though).

Honestly, I am not an uC-expert at all, but I have friend who is. However he
told me that he is not so much interested about the CBM part, so he can help
if I figure out the "commodore side" of the story. After all, my hope that I
can learn something new from this try at least ...

The reason I'd like decent transfer rate between C64 (or DTV) and the uC:
I'd like to use an uC with ethernet capabilities later.  Though there are
ethernet solutions (like TFE or RR-Net) for the C64, I always felt that I
want something like this for DTV too, where there is no solution for the
problem (and you don't have an std C64 bus at all - but you have some kind
of user port at least, even if it's not the very same).  As DTV has many
memory, and I already experimented with some kind of "advanced OS"
(multitasking etc) for the DTV, it would be really nice to have TCP/IP too
(I've already have a partly working stuff like that for RR-Net on C64, as
uIP seems to be complicated for me - and it's C - and I haven't heard too
much about IP65 when I started that project).

But currently I want to focus only a solution which provides good transfer
rate between C64 and a uC without thinking other topics.

- Gábor

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