ATLAS TDAQ system integration and commissioning

The ATLAS detector will be exposed to proton proton collisions at a center of mass energy of 14 TeV with the bunch crossing rate of 40 MHz. A three-level trigger system has been designed to reduce this rate down to the level at which only interesting events are fully reconstructed. The level 1 trigger reduces the rate down to 75 kHz via custom-built electronics. The Region of Interest Builder delivers the Region of Interest records to the second level trigger which runs the selection algorithms with the commodity processors and brings the rate further down to ∼ 3.5 kHz . Finally the event filter reduces the rate down to ∼ 200 Hz for permanent storage. We review the trigger and data acquisition architecture and its in situ commissioning using almost full detectors. Results on system functionality and performance based on the cosmic data, early experience on LHC beam in 2008 and preselected simulated events are presented.