Performance of the CMS ECAL data acquisition system at LHC Run II

During 2017, the Large Hadron Collider has provided p-p collisions up to an integrated luminosity of 50/fb. The CMS detector was able to record 90.3pct of this data. The CMS electromagnetic calorimeter (ECAL), made of 75848 scintillating PbWO4 crystals and a silicon-lead preshower, has achieved an excellent data collection efficiency thanks to the reliable ECAL data acquisition (DAQ) system. The ECAL DAQ system follows a modular and scalar schema the crystals are divided in sectors, each controlled by 3 interconnected boards. These boards are responsible for the configuration and control of the front-end electronics, the generation of trigger primitives for the central CMS L1 trigger, and the collection of data. A multi-machine distributed software configures the electronic boards and follows the life cycle of the acquisition process. With the increase of instantaneous luminosity in Run 2, the number of occasional errors due to radiation effects on the front-end electronics has increased. The ECAL DAQ has been improved to automatically detect and recover from these errors. We describe the ECAL DAQ system, its automatic recovery procedures, monitoring tools, and system performance.