Improve and constrain the use of the external triggers in the LPM and the ICI

The LPM hardware has four trigger-related lemo connectors on its front panel:

• TR0 and TR1
• AUXA and AUXB

The TR0/1 lines are connected to NIM input stages, whereas the AUXA/AUXB lines are connected straight to a TTL I/O bank on the FPGA. (Link to 'TCDS FMC 2SFP LEMO' FMC details in EDMS: https://edms.cern.ch/nav/P:EDA-02708:V0/P:EDA-02708:V0.)

The iPM and iCI firmware blocks each contain two external trigger input ports. Enabling/disabling these triggers is part of the respective (i.e., iPM and iCI) configuration. These firmware trigger ports are connected to the selected physical external trigger inputs, which are (optionally inverted versions of) either the TRx or the AUXx inputs. This selection is part of the LPM configuration.

There are two potential issues with the above:

• Even though an iCI can be configured to listen to an external trigger, it has no control over the external trigger selection. This can lead to confusion. (At the same time it should be considered that iCI-only runs are expert jobs.)
• With the introduction of the second iPM (firmware block) in the LPM (hardware) there is a potential for conflicts, because the current implementation of the LPMController will try to control both external trigger input selections. With two LPMControllers connected to the same LPM hardware, this can lead to confusion.

Proposal:

• Remove the external trigger inputs from the ICIController software, in order to avoid confusion in iCI-only runs.
• Divide the control over the external trigger inputs over the two LPMControllers controlling the two iPMs in the LPM: iPM #1 gets TR0 and AUXA, and iPM #2 gets TR1 and AUXB.