The information here is mostly obsolete. Easiest way to check this is opening the MachineDataFile in a text editor.
Dev1 is the auxiliary board, PCIe-6323 controlling the Piezo and the Pockels cell, receiving external trigger.
Dev2 is the imaging board, PCI-6110 controlling the scanners and receiving PMT output.

Our single NI 6110 S series board is connected via a BNC2110 to the various inputs and outputs required to control, synchronise and acquire data on the 2P system.

The details from the ScanImage docs are here but I always find them indigestible.

For triggering, there are 2 modes: external and internal. In either case a wire has to relay a signal to a digital input pin on the DAC board. For internal triggering, ScanImage generates a pulse on one of the digital outs (which must therefore be connected to an input port – usually just by a little patch wire). For external triggering, the trigger must be connected to a BNC on the board, which in turn must be "patched" with some wire to a digital input.

====== External triggering ======
  * The ITC-18 TTL Out 0 is connected by a BNC cable to the User 1 BNC on the 2110 box.
  * User 1 BNC is patched to PFI 1 digital input. ScanImage listens to this when it is in external triggering mode.


  * Shutter is connected to User defined signal 2, which is then wired to P0.2

====== Internal triggering ======
  * ScanImage supplies a trigger on P0.0
  * ScanImage listens on PFI0
  * so these two must be connected together
  * PFI0 has its own dedicated BNC and P0.0 is on the patch board
    * You can also connected P0.0 to one of the user ports if you feel like it but I don't see the point (you can split the BNC connector on PFI0)