Virtex-4 configuration details

Hello,

I'm currently looking at the virtex-4 configuration details and have a
question about FDRI writes in the virtex4.

My reference point is the virtex-2 configuration. In the virtex-2
configuration, FDRI writes always include a pad frame (except in the
MFWR write case, but that's not what i'm looking at).

Virtex-4 documentation makes no hint at such a frame. Indeed,
uncompressed bitstreams show that the exact number of frames are
written to the FDRI -- no pad frame there.

However, compressed bitstreams do not show such behaviour: FDRI writes
of isolated configured portions of the design seem to show pad frames
being written (the last frame's FAR value has already been programmed
earlier). I'm left guessing that either the bitstream programs some
frames twice (unlikely), or there's some machine state condition that
i'm missing, which indicates whether or not pad frames are needed
during FDRI writes on the virtex-4.

Can someone enlighten me on this?

Kind regards,
Jean-Baptiste