TIM has a register for trigger type for triggers sent from TIM.
In Stand-Alone mode TIM is programmed with the TType to send to the RODs (12 bits). In Run-Mode TIM gets 8 bits from the TTC (via the front-panel opto-fibre) and adds 4 bits (user configuable data) to make the the TType sent to RODs.
ROD Registers
Registers in the ROD that refer to trigger type.
The ROD event traps can select ATLAS, TIM or ROD specific events.
The Router also has the same toggles, presumably for selecting events for the S-link.
I presume the selection is made based on a match to three numbers stored in the RTR_SLNK_ATLAS_DUMP_MATCH registers.