Master Clock Requirements to Support the
  Trigger Frameworks and the Level 1 Calorimeter Trigger in Run II
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                                                           Rev. 18-MAR-1996


The Run II Trigger Frameworks and L1 Cal Trig will require many more Master
Clock signals than their Run 1 counterparts.  For Run II, we need the
following quantities of signals generated by the Master Clock System.

For the Run II Serial Command Link (SLIM modules)

      6 Sequencer signals, 2 copies of each signal
      2 copies of the 53 MHz RF

For the Run II Frameworks

      15 Sequencer signals, 6 copies of each signal
       6 copies of the 53 MHz RF.

For the Level 1 Calorimeter Trigger

      20 Sequencer signals, 1 copy of each signal


Why such a big increase in our requirements on the Master Clock ??

   During Run I the Framework and Cal Trig equipment used only 2 Sequencer
   signals.  We used these two signals as the control inputs to MSU built
   clock generators that were part of the Framework.  We ran 4 of these MSU
   clock generators; each one producing 32 outputs.  Almost all of these
   128 outputs were in use during Run 1.

During Run II we want/need to scrap the MSU clock generators.  This is why
we need so many more Sequencer signals in Run II.

Clearly this is going to be a large amount of Master Clock equipment to
generate all of these signals.  Order of magnitude I think this will
require two new crates worth of Master clock equipment.

   One crate could hold a Sequencer and 8 Selector Fanout Modules for the
   Framework signals and an additional 2 Selector Fanout Modules for the
   Serial Command Link signals.

   The other crate could hold a Sequencer and 5 Selector Fanout Modules for
   the L1 Cal Trigger.

We would like to locate this Master Clock equipment on the 1st floor MCH
near the Framework and Cal Trigger equipment.  Perhaps it can go in the
"M125" rack that currently holds the 192 scalers for 36x36 per bunch
monitoring.  Locating this Master Clock equipment on the 1st floor
minimizes the amount of bulk cabling between the Selector Fanouts and the
trigger equipment.  I don't know if there is a problem bring the PCLK,
MCLK, and SYNC signals down from the PCC on the 2nd floor to Sequencers on
the 1st floor.



Recall how the world is put together:

Phase Coherent Clock (PCC) --> Sequencer (SEQ) --> Selector Fanout Module (SFM)

Up to 13 Selector Fanouts in a crate.  Each SFM selects 4 Timing Lines
(TL's) from the sequencer and fans out each of these TL's through 3
outputs.  Thus a SFM has 12 outputs.

D0 Notes:   PCC  D0 Note #1214
            SEQ  D0 Note #927
            SFM  D0 Note #926