P2 is 50-pin high density, which we route to a 50-pin mass terminated
two-row 100 mil header.

Mumbering according to the sequence of wires in a
ribbon cable, if you look at the solder side of the
male connector, you see:

1     26
  2     27
3     28
  4     30
 .     .
 .     .
 24     49
25    50

This is the pin numbering used on the connector documentation
and on our schematics for both the digital and analog PC boards.
But if you look at the wire numbers of a ribbon cable used
to implement this (especially if it's one of the nice color
coded cables) you would count like this:

1     2
  3     4
5     6
  7     8
 .     .
 .     .
 47    48
49    50

Now for the hacks:

Pin 17 (cable wire 33) is shorted on the LLRF digital board.
Pin 44 (cable wire 38) is used in its place.  Also, we switched
from using the current-mode DAC output (pins 26 and 3) to
voltage-mode buffered output (pins 1 and 27) to drive the
I/Q modulator.

P2, digital board               J24, analog board
     Pin 1 -----       (Ground) ----- Pin 1
     Pin 26     \-------------------- Pin 26
     Pin 2              Ground ------ Pin 2
     Pin 27 ----       (Ground) ----- Pin 27
     Pin 3      \-------------------- Pin 3
     Pin 28             Ground ------ Pin 28
     Pin 4 -------------Ground ------ Pin 4
       .                                .
       .                                .
     Pin 17       /------------------ Pin 17
       .         /                      .
     Pin 44 ----/                     Pin 44
       .                                .
       .                                .
Grounds on J24 pins 2, 28, and 4 need to be connected
in this cable.  Pins 1 and 27 can be left hanging, as
they will be connected to ground by the analog board.
P2 pins 26, 2, 3, and 28 need to be "No Connect".
This diagram is drawn in ribbon cable order.
Dangling cables must be protected from accidental shorts
to ground.

The four status LED's also need to tap off of these pins.
 name    schematic pin    cable wire
LED_1        38              26
LED_2        39              28
LED_3        40              30
LED_4        42              34
return       41              32
We actually added a 4-pin 100 mil header to the board, bypassing
the ribbon cable, and used system ground for the return path.

Last update: 6/5/2002 LRD