The ATLAS Level1 endcap muon trigger selects potentially interesting events containing muons with the transverse momentum (pT) greater than 6 GeV/c from 40 MHz proton-proton collisions. The system consists of 3,600 Thin Gap Chambers (TGCs) and the total number of readout channels is 320,000. The trigger logic is based on the coincidence between seven layers of TGCs. All processes are performed on fast electronics within 2.5 μs. To be ready for the first beam, we have succeeded in sending trigger signals of cosmic-ray muons with the synchronous operation at 40 MHz and fine signal timing adjustment. We report on the status of the commissioning and the results from the combined runs with all ATLAS detectors.