Ruprecht-Karls-Universität Heidelberg

Synchronization of Front-End Electronics in a Data Acquisition Interconnection Network

Bachelor Thesis by Philipp Schaefer


The CBM network is an unified Data Acquisition (DAQ) interconnection network for the Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt. An important feature of this network is that all network abilities are implemented with only one single bidirectional fiber link. This feature saves cable costs and is realized by sending all three existing traffic classes via this link. Moreover, the network provides a synchronization mechanism using Deterministic Latency Messages (DLM) for precise time synchronization.

In the context of this bachelor thesis a front-end synchronization mechanism was implemented. It autonomously measures the latency between a planned HUB ASIC and Front-End Electronics (FEE) and configures appropriate delays to the output lanes. Due to this delay adjustments, DLMs reach all the FEEs at the same time. This is necessary to reset timing counter values and achieve a common time synchronization. Moreover, data can be matched to their FEEs by time stamp and measured latency. Further it is ensured, that data coming from the FEEs is phase aligned to the internal HUB ASIC bit clock and thus sampled correctly.


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