Ultra  FLVC2104  BGA  Geometry   Revision Two
    -----------------------------------------------


                                           Original Date:  26-Jan-2016
                                            Current Date:  29-Jul-2016


The goals of this version of the geometry for the UltraScale
XCVU125-1FLVC2104I  are:

 - Implement a basic 4 quadrant geometry with an appropriate
   default  SMD Pad plus Via  pin/pad stack for each quadrant.

   The will be standard: NE, NW, SW, SE  angled pin/pad stacks
   that are placed based on the X,Y location of their Via.


 - Around the perimeter  (aka the outer most row  Except at
   the 4 corners)  use  SMD Pad plus Via  pin/pad stacks that
   run: NNE, ENE,  ESE, SSE,  SSW, WSW,  WNW, NNW.   In these
   8 pin/pad stacks the vias are placed 0.3mm further out away
   from the periphery.

   These pin/pad stacks are also placed by the X,Y location
   of their Via.  These 8 pin/pad stacks have a slightly
   longer dog-bone that is used to give more clearance
   around the periphery of the pin field.

   These perimeter ring pin definitions are held in 4 hand
   codes files.  There is a version of these files that have
   long dog-bone pin/pad stacks at all perimeter ring pins
   and a version that has long dog-bone pin/pad stacks at
   all perimeter ring pins  except  the perimeter MGT pins
   and the pins on either side of MGT pins.

   All of these perimeter ring pin definition file have
   filenames of the form:

      flvc2104_rev__2__pin_list_north  [south, east, west]


 - At the 4 corners this package does not have any pins.
   Thus we do not need special pin/pad stacks with long
   dog-bones for use at the corners.  Thus we do not need
   pin/pad stacks for this package of the form:
   FNE, FSE, FSW, FNW   i.e. longer in both X & Y by 0.3mm.


 - Remove the  SMD Pad plus Via  pin/pad stack from all
   unused pins on the device and replace them with just
   a default  SMD Pad Only  pin/pad stack.

   * For now a list of device pins that will have an
     SMD Pad Only  pin/pad stack can come from the single
     pin nets for U1 in the sorted net list.

   * Eventually we also need to use the  SMD Pad Only
     pin/pad stacks for device pins with nets that escape
     on the top layer of the PCB.

     - The signals that connect on the top side and thus
       need only an SMD pad are  hand coded  into text
       files.   These are merged with the list of pins
       that make no connection  and then  all of these
       pins are give SMD pads only.

     - An example of signals that make a top side connection
       and thus want only an SMD pad are the perimeter MGT
       signals.   The pin innolved with the MGT perimeter
       signals that want only and SMD pad are listed in the
       file:

         pin_numbers_of_smd_pad_only_mgt_pins.txt

   * The  SMD Pad Only  pin/pad stacks are placed by the
     X,Y location of the SMD Pad  (not offset to the Via).

     I want to figure out how to place the  SMD Pad Only
     pin/pad stacks  without keeping 2 pairs of X,Y
     coordinates for each of the 2104 device pins.


What is NOT being attempted so far in this Revision Two
geometry is to worry about the many different types of 
SMD Pad plus Via  pin/pad stacks that will eventually be
needed for the active pins in each quadrant, e.g.

  normal signal with normal via,
  normal signal with blind via,
  high-speed signal with small via,
  high-speed signal with small blind via,
  power/ground with thick dog-bone and normal via



Instructions:

 - Run the script   aa_build_rev__2__basic_flvc2104_geom.sh

   to build the  standard basic  Rev 2  version of the
   the flvc2104 geometry.   Every pin on the device will
   have a  Pad and Via  pin/pad stack with the via offset
   from the pad an appropriate distance for either the
   main field of pins  or  for the outer most ring
   of pins.  All of the vias are the same standard signal
   via.


 - Run the script   aa_build_rev__2__tailored_flvc_2104_geom.sh

   to build a  tailored  Rev 2  version of the flvc2104
   geometry.  In this case all of the U1 FPGA pins that
   are indicated as  Single Pin Nets  in the  Sorted NetList
   file   and   in the file

     pin_numbers_of_smd_pad_only_mgt_pins.txt

   will have  SMD Pad Only  pin/pad stacks.


 - Note that this script requires you to have made a copy
   of the  Rev 1  flvc2104 geometry,  to have extracted from
   it just the  2104 pin definitions  and to have put it
   in a file in this directory called:

      full_field_smd_pads_only_pin_definitions.txt