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                59.1    INTRODUCTION . . . . . . . . . . . . . . . . . .  59-1
                59.2    DESCRIPTION  . . . . . . . . . . . . . . . . . .  59-1
                59.3    SPECIFICATIONS . . . . . . . . . . . . . . . . .  59-2
                59.3.1    Inputs:  . . . . . . . . . . . . . . . . . . .  59-2
                59.3.2    Outputs: . . . . . . . . . . . . . . . . . . .  59-2
                59.4    CAMAC FUNCTIONS  . . . . . . . . . . . . . . . .  59-2
                59.5    DRAWING PACKAGE NUMBER . . . . . . . . . . . . .  59-3
                59.6    RESPONSIBLE ENGINEER . . . . . . . . . . . . . .  59-3

                                      CHAPTER 59
                        VIDEO DIGITIZER CLOCK INTERFACE (VDCI)

        59.1  INTRODUCTION

        The VDCI is a single-width CAMAC module.  It is  used  in  conjunction
        with a transient waveform digitizer such as the TRANSIAC model 2008 to
        digitize video (RS-170) information.  The purpose of this module is to
        limit  unnecessary handling of useless information in the digitizer by
        selecting a critical part of the picture for digitizing.   The  module
        does  this  by  producing  bursts  of  clock pulses which instruct the
        waveform digitizer when to sample.  The horizontal and vertical start,
        stop, and resolution are settable and readable through CAMAC.

        59.2  DESCRIPTION

        The vertical start and stop coordinates are loaded into counters  from
        their  respective latches during the video's vertical sync pulse.  The
        vertical start counter counts lines until  the  designated  region  is
        reached,  then  enables  the  digitizer's  clock.   The  stop  counter
        continues to count until it drops out of the designated  region,  thus
        disabling the clock.
        The horizontal counters are loaded in the same manner as the  vertical
        except  that  they  begin  from  the horizontal sync pulse.  The start
        counter counts clock pulses until the designated  region  is  reached,
        then  enables  the  digitizer's  clock.   The  horizontal stop counter
        continues until out of the region on that  line,  at  which  point  it
        disables  the  clock.   Vertical  coordinates  are set from 0->255 and
        horizontal coordinates are  0->511.   The  stop  coordinates  must  be
        larger  than  the  start  in  both  the  vertical  and  the horizontal
        directions.
        The vertical and horizontal resolution  counters  continuously  reload
        themselves  from  their  respective  latches  at the end of each count
        sequence.  The  vertical  resolution  is  gated  with  the  designated
        region,  then with the horizontal resolution which has been gated with
        the  pixel  clock.   The  culmination  of  all  this  determines   the
        digitizer's clock.



        VIDEO DIGITIZER CLOCK INTERFACE (VDCI)                       Page 59-2


        59.3  SPECIFICATIONS


        59.3.1  Inputs:

              o  Video In -- Video signal from camera terminated in 75 Ohms.
              o  Beam Trig -- Beam related negative edge  trigger  NIM  signal
                 terminated in 50 Ohms.

        59.3.2  Outputs:

              o  Video Sum -- The digitizer clock is  summed  with  the  video
                 signal  then  run  in to a TV monitor to give a "highlighted"
                 visual representation of the area being digitized.
              o  Video Out -- The video signal is buffered through  a  current
                 amplifier which feeds the digitizer's input signal.
              o  Stop Trig -- When an F25*A0 is issued to the module, it waits
                 for a beam trigger and a vertical sync, then sends a positive
                 edge trigger TTL pulse to the digitizer.  This  triggers  the
                 digitizer  and  insures  that  memory  contains the last beam
                 pulse.
              o  Dig.  Clk --  Positive  edge  trigger  TTL  clock  tells  the
                 digitizer when to sample the input signal.  50 Ohm driver.

        59.4  CAMAC FUNCTIONS

              o  F0 A0:  Bits 0->8 reads the horizontal start coordinate
              o  F0 A1:  Bits 0->8 reads the horizontal stop coordinate
              o  F0 A2:  Bits 0->7 reads the vertical start coordinate
              o  F0 A3:  Bits 0->7 reads the vertical stop coordinate.
              o  F0 A4:  Bits 0->3 reads the horizontal resolution.
              o  F0 A5:  Bits 0->3 reads the vertical resolution.
              o  F16 A0:  Bits 0->8 writes the horizontal start coordinate.
              o  F16 A1:  Bits 0->8 writes the horizontal stop coordinate.



        VIDEO DIGITIZER CLOCK INTERFACE (VDCI)                       Page 59-3

              o  F16 A2:  Bits 0->7 writes the vertical start coordinate.
              o  F16 A3:  Bits 0->7 writes the vertical stop coordinate.
              o  F16 A4:  Bits 0->3 writes the horizontal resolution.
              o  F16 A5:  Bits 0->3 writes the vertical resolution.
              o  F25 A0:  Starts the stop trigger process.

        59.5  DRAWING PACKAGE NUMBER

        233-903

        59.6  RESPONSIBLE ENGINEER

        D.  G.  Brown