Re: Black box again

Hi Jon,

Some comments below:


Jon Elson wrote:

>
> Alan Marconett KM6VV wrote:
>
> > Hi Jon, Ballendo,
> >
> > I have noticed, that while you can get a parallel port board (SIIG) for
> > the PCI bus, it may (always?) put the address not at 278/278h, but at
> > something like C400h! And DOS won't recognize it! Fine for Windoz, but
> > not good for "older stuff" (like me). Perhaps someone can shed more
> > light on this subject!
> >
> > On the other hand, USB is called marginal on Windoz95, and nonexistent
> > on 3.1 and DOS. Not that I mind Windoz98 2nd Ed, but I still like/use
> > DOS.
>
> Well, this isn't a problem for special purpose devices, as we control all
> the software, we can adapt to whatever address things show up as.
> Anyway, the parallel port address is configured by a line in the .ini
> file for EMC, so it is user settable.

From what I've seen, the problem is more that DOS can't see an LPT at
C400h. The port doesn't appear to be there at all, it simply doesn't
show up!

>
> > Jon, I know you have your "black box" running already (and nearing
> > production?), but what are your thoughts about USB control? Any
> > possibility?
>
> It is IN production, although there are only a few units installed so
> far. The problem with USB is the huge overhead for protocol on the
> CPU side, as well as the requirement of having a processor on the
> device side. There is no processor needed in my current PPMC design,
> it is all done with CPLDs and FPGAs. There was a lot of info indicating
> USB was not a good choice for real time things that needed a lot of
> transactions per second. We need to handle at least 1000 servo cycles
> a second, and some users might demand more. My boards should be able to
> handle 10 KHz without any trouble, and complete the full servo cycle
> (read current position, compute new velocity and load velocity) in
> about 25 uS when I employ all the IEEE-1284 bells and whistles. I'm
> doing about 50 uS right now, using basic functions without much
> optimizing.

So you're doing full 1284 xfers (handshake managed by hardware)?

Alan KM6VV