To make this work correctly, I think you would need
some hardware "glue"
that would detect each data word and then immediately assert a NRFD. A few
microseconds later it would release the line and allow the next data word
to
be transmitted. This hold-off would need to be just long enough to allow
the
micro to process the data. Something as simple as a one-shot might do the
trick.
Or use a faster processor :) Or a CPLD comes to mind :)