Diagnostic system of the RPC muon trigger of the CMS detector - design and test beam results

The RPC muon trigger electronics of the CMS detector performs a number of tasks: synchronization of detector signals, optical data transmission from the detector to the trigger electronics, pattern recognition, muon momentum measurement, selection of track candidates. For the diagnostic purposes, as well as for the calibration and real-time monitoring of the RPC detectors and electronic hardware, a set of flexible diagnostic modules was designed and implemented into the FPGAs on which the trigger electronics is based. These include: multi-channel counters, timing histograms, test pulses, and data spying ("snapshots" of the data stream). Tests results presented in this paper, including test with LHC-like muon beam, illustrate the performance and usefulness of these diagnostic modules.