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                10.1    FRONT PANEL  . . . . . . . . . . . . . . . . . .  10-1
                10.2    FUNCTIONAL DESCRIPTION . . . . . . . . . . . . .  10-1
                10.3    CAMAC COMMAND SUMMARY  . . . . . . . . . . . . .  10-2
                10.4    POWER SUPPLY REQUIREMENTS  . . . . . . . . . . .  10-3
                10.5    DRAWING PACKAGE NUMBER . . . . . . . . . . . . .  10-3
                10.6    RESPONSIBLE ENGINEER . . . . . . . . . . . . . .  10-3

                                      CHAPTER 10
                         DIVIDED DEMULTIPLEXED TRIGGERS (DDT)

        10.1  FRONT PANEL

              o  Double Width CAMAC Module
              o  Two "NIM INPUT" LEMO connectors  to  receive  PDUII  Triggers
                 from the STBII
              o  Four  "KICKER  TRIGGER  OUT"  LEMO  connectors  to  send  the
                 PDUII/STBII NIM Triggers to Kickers
              o  One "DIGITIZER  TRIGGER  OUT"  LEMO  Connector  to  send  the
                 PDUII/STBII NIM Trigger to Video Digitizing Equipment
              o  One "VIDEO SELECT OUT" Four-conductor  LEMO  Connector,  with
                 RS-422  signals indicating which Kicker Trigger Out will next
                 be triggered

        10.2  FUNCTIONAL DESCRIPTION

        The DDT receives, through one of the two, CAMAC selected, "NIM  INPUT"
        LEMO  connectors, a standard SLC timing trigger (a 67.2 nsec NIM pulse
        from a PDUII, buffered by an STBII).  This trigger is used to clock  a
        programmable modulus (divide-by-N) counter.  When the counter has been
        clocked half way (N/2) to it's terminal count, a modulo-4  counter  is
        incremented.   The outputs of this modulo-4 counter are used to select
        which "KICKER TRIGGER OUT" will  be  activated  when  the  divide-by-N
        counter  is at it's terminal count.  The state of the modulo-4 counter
        is made available on the "VIDEO SELECT OUT" LEMO connector, as  RS-422
        signals,   to  be  used  to  multiplex  video  signals  to  digitizing
        equipment.  When the divide-by-N counter is at  it's  terminal  count,
        the  next  received  timing  trigger will be routed to the appropriate
        "KICKER TRIGGER OUT" LEMO connector, as  a  NIM  signal.   The  timing
        trigger is also sent to the "DIGITIZER TRIGGER OUT" LEMO connector.
        In summary, the DDT module will sequentially  route  one  of  every  N
        PDUII/STBII triggers to the four "KICKER TRIGGER OUT" connectors.



        DIVIDED DEMULTIPLEXED TRIGGERS (DDT)                         Page 10-2


        10.3  CAMAC COMMAND SUMMARY

              o  F(0)A(0) R2-R1 reads the modulo-4 counter,  indicating  which
                 KICKER  TRIGGER OUT will next be energized.  The state of the
                 modulo-4 counter is also made available as an  RS-422  signal
                 pair on the VIDEO SELECT OUT connector.
              o  F(0)A(1) R1 indicates which NIM INPUT has  been  selected  as
                 the trigger source.
              o  F(1)A(0) R9-R1 reads out the modulus  N  of  the  divide-by-N
                 counter.
              o  F(1)A(0) R9-R1 reads out the current state of the divide-by-N
                 counter.
              o  F(16)A(0) W2-W1  loads  the  modulo-4  counter,  selecting  a
                 particular  KICKER  TRIGGER  OUT channel.  This value is also
                 made available as an RS-422 signal pair on the  VIDEO  SELECT
                 OUT connector.
              o  F(16)A(1) W1 selects which NIM INPUT is to  be  used  as  the
                 trigger source.
              o  F(17)A(0) W9-W1 sets  the  modulus  (N)  of  the  divide-by-N
                 counter.  The maximum allowed value is 360.  When the modulus
                 is set to 0, triggers are  prevented  from  being  generated.
                 When  the  modulus  is set to 1, every NIM INPUT is routed to
                 one of the KICKER TRIGGER  OUT  outputs.   However,  in  this
                 case,  the  modulo-4 counter is clocked with a 50 msec pulse,
                 allowing sufficent time to digitize an image before selecting
                 the  next  KICKER  TRIGGER  OUT and VIDEO SELECT OUT channel.
                 When the modulus is in the range from 2 to 360, the Nth pulse
                 is  routed  to the selected KICKER TRIGGER OUT channel.  When
                 the modulo-N counter  is  at  the  value  N/2,  the  modulo-4
                 counter  is  clocked,  allowing  sufficent time to select and
                 digitize a video channel.  When the modulo-N  counter  is  at
                 the value N, a selected KICKER TRIGGER OUT channel is pulsed.
                 The modulo-N counter counts from 1 to N (not 0 to N-1).
              o  F(24)A(0) disables the modulo-4  counter.   This  means  that
                 every  Nth input pulse will only go to the F(16)A(0) selected
                 KICKER TRIGGER OUT channel.
              o  F(26)A(0) enables the  modulo-4  counter,  allowing  the  Nth
                 input  pulse  to  be  distributed sequentially to each of the
                 KICKER TRIGGER OUT channels.
              o  X = Q = 1 is returned for all of the above CAMAC operations.



        DIVIDED DEMULTIPLEXED TRIGGERS (DDT)                         Page 10-3


        10.4  POWER SUPPLY REQUIREMENTS

        +6V @ 1.0A
        -6V @ 2.0A

        10.5  DRAWING PACKAGE NUMBER

        XXX-XXX

        10.6  RESPONSIBLE ENGINEER

        E.  Linstadt