MPC823E USB controller - delay gates necessary?

[Josh Horvath]

To follow up on my original message, it appears that the delay gates are
indeed required for proper host mode operation on the 823e.  Using the
PDIUSBP11A transceiver, we measured about 6-8ns of skew between the single
ended and differential receive lines.  This is apparently too close to the
+8ns limit stated in the MPC850 device errata.

So you may get a lucky transceiver/processor combo that will work, but most
likely you'll need the delay gates on the differential receive pair to get
host mode to work reliably.

-Josh

Josh Horvath wrote:
>
> The device errata for the MPC850 includes the CPM17 bug that states delay
> gates are necessary on the USB pins.  The MPC823E errata sheet does not
> mention this bug.
>
> I recently read the message by Christian Schroeder about getting the USB
> controller working on the TQM823L board (with an 823E processor).  He states
> that the delay gates are necessary.  Is this true?
>
> I've got a custom 823E board that doesn't include these gates and I'm having
> trouble getting the controller working, and it's not totally clear to me if
> it's a hardware or software problem.
>
> Thanks,
> -Josh
>

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