Euroball III Data Acquisition
Event Builder
Super-Event fragment buffers of the same events collected in the Readout Units
are sent in parallel via the FCS switch to the same destination processor to
be analysed. The fragments are tagged with the event number within the ROCOs.
The event builder function includes tasks such as:-
- Basic consistency checks on the event fragments. The raw data format
contains redundant information for security and this can be checked for
self consistency to detect possible hardware errors during data readout.
- Using the event number within each fragment complete events are
constructed. Further checks can be performed on the complete event to ensure
correct functioning of the frontend electronics and readout mechanism. For
example the data received can be checked against the hardware setup to
detect readout errors.
- The fragment tokens are removed at this stage and the
formatted complete event is now in a more compact format than the raw data.
- Statistical information is produced so that a constant check can be
kept on the quality of the raw data and alarms produced if the error rate
exceeds reasonable levels.
All data sources (ROCOs and FERA masters) are required to generate an
event fragment even if it contains no data. This is important for the
event construction since it is possible to detect a missing event fragment
or malfunctioning data source
which would not be the case if empty fragments were not required.