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LCLS-II DAQ

LCLS-II DAQ State Machine

Description of States

  • Reset: initial state of the system, jump to this state from any other state to recover from (some) errors
  • Unallocated: the state of the system before any detectors are allocated to participate in the DAQ.  The "roll call" transition is used (often repeatedly, on a timer) to query the available detectors, which can take some time if not all detector executables are running yet
  • Allocated: the state the system goes into after the user has selected which detectors they would like to use in the DAQ
  • Connected: the state of the system after all "connections" are made.  This idea of "connection" is general: it represents network connections (infiniband, ethernet, zeromq) as well as connections of the timing system readout groups, for example
  • Configured: the state of the system after configuring all selected detectors (often a time-consuming step) or ending a run.
  • Starting: this state is used to mark boundaries between scan-steps (where a motor is moved in coordination with pausing the DAQ)
  • Paused: a state where the triggers to the system are disabled
  • Running: the state where the DAQ is receiving per-shot data ("L1Accept").  The DAQ also receives a low rate (~1Hz) of SlowUpdate transitions which are used to record slow epics data and other slow data (time tool backgrounds)
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