We have chosen to assign trigger type as the lowest type to fire,
when multiple types fire. In the XMLU, it is possible to set multiple
output bits: for example, a (left TOF and Cerenkov) AND (right TOF) will
set output bits 0 and 6. In the scalers, PHYS0 and PHYS6 both count. CODA
will assign that to trigger 1. This choice was made ages ago so that we
could just read the singles rate off the scalers.
I believe that in the case where one of the bits is prescaled in
the Trigger Supervisor, the prescaling happens first, and then the
resulting bit pattern is checked for the lowest set bit. So if bits 2 and
6 were set out of the XMLU, and the TS prescales bit 2 heavily, then most
of the time the event will be assigned to trigger 7. Only rarely will the
event be trigger 3.
Because the PHYSn scalers count before any TS prescaling, and
before any TS check of multiple set bits, the trigger rate will always be
less than or equal to the sum of PHYSn, even for the level 1 trigger
configuration (which has prescales) or the cosmic configuration (which
reduces multiple set bits to the lowest set bit).
Does all of that look consistent with what you see in the data
recorded to disk?
Karen
At 03:48 AM 5/15/2004 -0400, Chris Crawford wrote:
>hi karen,
> a question about triggers: are the different trigger types
> independent? i worry that triggers 4,6,7 are lower priority than highly
> prescaled triggers, so that if one of these triggers coincides with
> trigger 3,5, it will be prescaled even though its prescale factor is set to 1
>--thanks, chris
This archive was generated by hypermail 2.1.2 : Mon Feb 24 2014 - 14:07:31 EST