About the path data...

The main thing to remember about paths is that EVERYTHING on
a ControlLogix is a ControlNet Network - including the
backplane.  All communications cards are bridge devices with
multiple internal ports.

For example, a ControlNet card (1756-CNB) has 3 interal ports,
#1 is the backplane, #2 is channel A and #3 is channel B.  The
Ethernet card is simular (bridges from the ethernet port to
the backplane) - port #1 is the backplane and port #2 is the
ethernet channel.

On the backplane, the slot number is the controlnet device ID.
Slot 0 is device #0, slot 5 is device #5, and so on.

Creating the path data is the simple aggregation of this data
in a sequential form.  You follow the signal path physically, 
using that data to enumerate the path data.

For example, assume you have 2 racks - rack number 1 has a CNB in 
slot 0, a CPU in slot 1, and an ENET in slot 3.  Rack #2 has a CNB
in slot 0 and slot 1 has the CPU.  The two racks are connected by 
ControlNet.  Rack 1 is address 8 and rack 2 is address 9 on the 
ControlNet network.  Your path data to talk to rack 2 through 
rack 1 via ethernet would look like this:
01, 00, 02, 08, 01, 01

The first 01 crosses the ethernet->controlnet bridge.  The
following 00 addresses the card in slot 0 in the first rack.  The
02 addresses the second channel in that card (channel A on the
CNB card).  The 08 talks to device 08 on the ControlNet 
network.  The second 01 crosses the ControlNet bridge into the
backplane and the final 01 talks to the card (CPU) in slot 1.

Clear as mud?  :)

Ron Gage
