Documentation on the scaler-board inputs is kept

  a) in the RAT-board routing table, accessible through the online trigger pages

  b) on the scaler monitoring website

The routing table is more convenient in keeping track of history, the monitoring website is more convenient for the background.

Specifically, for 2013:

  a) http://www.star.bnl.gov/public/trg/run2013/ScalerRouterMap_run13.txt

  b) http://online.star.bnl.gov/scaler2013/documentation/scaler32map2013.pdf

As per b), board 1 serves ZDC-based local polarimetry.  Nearly all inputs are needed, if not essential.  The data are analyzed.  Any changes to this mapping will be very costly.

Boards 2 and 3 collect individual channels from the BBCs.  Board 2 contains all channels from BBC-East and a subset from BBC-West.  Board 3 contains all channels from BBC-West and a complementary subset from BBC-East.  These boards are used for BBC-based local polarimetry.  They can be used for 1-arm and 2-arm luminosity measurements with selectable acceptance, although this functionality has not been fully exploited in STAR so far.  Changes here will again be quite costly, in particular for bits 0-15; don’t do it.

Board 4 contains a minimal set of essential inputs for luminosity measurements.  The detector-live counting was not realized in run-13, so the 9-bits reserved for this purpose could, in principle, be repurposed.

Board 5 contains a minimal set of complementary inputs for luminosity measurements.  The bits reserved for detector-live counting can be repurposed to count the Roman-Pot tiles.  I propose to do so.

 
Board 6 is a spare.  It has typically contained the inputs from any of boards 1-5.  This has proven quite valuable in the past.  The usual caveats of using spares apply.
 

Bunch-crossing counting should be preserved in each scaler board, obviously.