Draft 0.1

        Global Level 1 Trigger to Level 3 Trigger

            Interface Specification
 
               7 August 1997


The Global Level 1 Trigger (GLT) counts trigger objects of each type
defined at Level 1 and generates decisions based on these counters.
The counter values are transmitted to the GLT Readout Module (ROM).
The ROM preserves this information, transmitting it downstream to
consumers such as the Level 3 trigger.  This specification outlines
the special needs of the Level 3 trigger (L3) as imposed on the GLT.


Minimal data content to be transmitted
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 * The object counts (see below for formatting)
 * Time stamp, relative to the arrival of L1A at the GLT

The order in which objects are listed must be known.  


Additional data derived in the ROM
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The need for other quantities is not foreseen.


Formatting
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Ideally, L3 would like to have the counts delivered as 17 integers; 
since counts go from 0-7, a single byte for each count would be acceptable.  
This would increase the GLT ROM's output from the present specification by 
about 150 bytes.