On Jul 22, 2004, at 1:10 PM, Wells, Charles wrote:

....... The real problem is that the
MPC850 USB controller was designed for target-mode applications and not
host-mode applications.  Host-mode in the MPC850 is, at best, an
after-thought.

That's true.  Having been a part of the early development of all of the
8xx
parts, there were lots of requirements that changed once the parts "hit
the street."

0. The MPC850 USB controller is neither of the popular USB 1.1
implementation models (UHCI or OHCI).

It's not the only one.  I think there are more embedded controllers that
are not UHCI/OHCI than those that are.  Since we work in the source
code world, it hasn't really been much of a problem.

..... I haven't timed it, but I suspect the microcode patch
has trouble meeting this spec. as well.  It does get a whole lot
closer than
a software-only solution, though.

The microcode patch works quite well.

There's a bunch of other detailed problems that I won't bore everyone
with.
Bottom line: Don't expect too much out of the MPC850 USB controller in
host-mode.

There are Linux versions of software that work fine in many
applications.
USB in general doesn't rate high on my list of engineering successes.
I'm never surprised when I plug something in to any kind of system
and it doesn't work.


	-- Dan


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