Date: Sat, 02 Oct 2004 13:01:14 -0400 (EDT)
From: GILMOR
Subject: new DDU format info

   Hi All,
At this beamtest we expect to use the  New DDU & DCC  boards
during the entire preiod.  Therefore you should know that
the  New DDU  has a few small format changes compared to the
old prototype.

First, there are 4 new 16-bit words at the beginning of every
DMB (i.e. CSC) data flow.  These 4 words each begin with a DDU 9
code (hex 9 code == DMB First Header word) and follow the format
as described on the DDU Input Format web page at URL
 http://www.physics.ohio-state.edu/~cms/ddu/ddu.html

Second, the event information contained in the DDU Trailer has been
rearranged to match the new CMS Common Data Format requirements.
For details, see the DDU Output Format web page at URL
 http://www.physics.ohio-state.edu/~cms/ddu/ddu2.html#tr

Third, the DDU Status reported by bit37 in Header3 and Trail-1
was redefined to indicate a TMB/ALCT CRC Error.  For reference,
this change is also reflected in the DDU Output Format web page.

Finally, in every Gigabit Ethernet packet we have added 2 bytes at
the end for the packet number.  A check has been built into the
new GbE driver to verify for each _Ethernet packet_ received
that the _packet number_ has incremented by one since the last
packet.  If you use the new driver then this feature is transparent
to the user and no changes are required.  Also, this new driver has
implemented memory mapping to improve performance in the PC.



The changes above are all that is needed to readout the  New DDU.
However, there are additional format changes introduced when the
readout is performed via DCC.  For this you should consult with
Jianhui Gu and see the DCC webpage at URL
 http://www.physics.ohio-state.edu/~cms/dcc/


Best regards,
	Jason