A measurement of the cross section of the Higgs boson production associated with a pair of top quarks (ttH) in proton-proton collisions at a center-of-mass energy of 13 TeV is presented. The measurement targets ttH final states with electrons, muons, and hadronically decaying tau leptons. Data used in this measurement are recorded by the Compact Muon Solenoid experiment at the CERN Large Hadron Collider in 2016 and 2017, corresponding to an integrated luminosity of 35.9 /fb and 41.5 /fb, respectively. The measured signal rate is 0.96+0.34-0.31 times the expected production rate in the standard model. The observed (expected) significance of the ttH signal is 3.2 sigma (4.0 sigma). A proposed FPGA-based track finding system for the CMS Level-1 trigger upgrade in preparation for the High-Luminosity LHC is also presented in this thesis.