Re: userport: C64, Plus4, others?

Hi,

if you start hardware development, beware that 6526 are usually very 
fragile.
you may need some replacement parts in case of problems.

for my experiment with 65xx I'm using a micro kim from Vince Briel.
http://www.brielcomputers.com/wordpress/?cat=5 
<http://www.brielcomputers.com/wordpress/?cat=5>
most of the replacement part are available from jameco
(I paid the 6532  $8).

in my first attempt to play with the hardware of my sx64 I burnt the pla...
but it was in 1984 and easy to replace...

--
didier

Le 05/03/2012 23:10, "Gábor Lénárt" a écrit :
> Hi,
>
> I'm thinking on starting to do some hw development. For some simple stuff, I
> am thinking to use C64's user port to exchange data with a microcontroller.
> As far as I can see, the bandwidth is quite OK, as CIA has some some
> handshaking pin (which is also connected on the user port), so the uC know
> if new data arrives or new data should be sent (previous byte is read by
> C64). With this theory, I guess the maximal transfer rate can reach what the
> CPU of C64 can do at all, and the handshaking is automatically done by the
> CIA itself. It sounds cool, however I am not sure. Anyway, I guess it can
> give the fastest availbale data transfer (faster only can be with some
> external DMA logic which disables the CPU of the C64, etc - not my business
> ... yet at least).
>
> 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? Is there any existing "example
> project" where I can study a solution like this? For starting point I'd like
> to have only the "data transfer part" via user port, and the uC would not do
> too much useful things, just some "accelerator" mode, like running programs
> and get/give input/output of that from/back the C64, later of course I'd
> like something more useful with the uC.
>
> I prefer user port, because it exists on other machines as well, not just
> C64. Like Plus/4. And it's my another question: it's not so clear for me:
> has the Plus/4 some similar handshaking possibilities via its user port as
> the C64/CIA has?
>
> I'd love to have something "for multiple machine" solution! Even if it means
> different phisical connectors for the actual user ports of these machines :)
>
> The last reason I would use user port (and not building a cartridge or so):
> user port exists on C64 DTV too (though I am quite sure there is no
> handshanking line there anyway ...), and there it's the only possibility to
> interface with a DTV (other then IEC of course).
>
> So in this way, some "userport" solution can be a quite fast, cross-CBM
> machine solution with some minor differences though "of course" but
> basically the same solution.
>
> Any feedback is welcome about my first seriously thought hw project to be
> started :-P
>
> - Gábor
>
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