Draft 0.1

        Fast Control and Timing System to Level 3 Trigger

            Interface Specification
 
               7 August 1997

The main interest of Level 3 (L3) in the Fast Control and Timing System
(FCTS) is in the generation of the Level 1 Accept decision.  The FCTS
receives the 24 individual trigger lines from the Global Level 1 Trigger 
(GLT) module and applies configured prescale factors to each line, adds 
some additional lines of its own, and arrives at the final Level 1 Accept 
decision.  These lines are transmitted to the FCTS Readout Module (ROM)
and available to downstream consumers.  A time is associated with the 
generation of the Level 1 Accept and also made available.


Minimal data content to be transmitted
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 * The 32 FCTS output lines, including 24 derived from the Level 1 output
   lines and 8 more added within FCTS.
 * The time associated with Level 1 Accept

L3 must know the definition of each line.



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


Formatting
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To be determined.