This page describes my limited knowledge on the theory of how the DAQ works.
DAQ flowchart
The DAQ seems quite complicated. Here's what I know about it:
1
Input signals received by the PTB
The PTB determines when a trigger should be sent out to all the detector subsystems to read out data based on beam signal, PMT, and CRT readings as input. The subsystem outputs are then stored on the subsystem computers.
2
PTB sends a signal to the NTB
When the NTB receives an event trigger from the PTB:
A new event is created
Data is pulled from the TPC readout electronics
The NTB tells the event builder to collect all coincident detector subsystem data from the subsystem computers.
3
Event building
Once instructed by the NTB, the event builder creates the event and saves it to disk.
The flowchart below explains this process a little better:
