The CMS Tracker Front-End Driver.

The Front End Driver (FED) is a 9U 400mm VME64x card designed for reading out the CMS silicon tracker signals transmitted by the APV25 analogue pipeline ASICs. The signals are transmitted to each FED via 96 optical fibers at a total input rate corresponding to 3 Gbytes/s. The FED digitizes the signals and processes the data digitally by applying algorithms for pedestal and common mode noise subtraction. The input data rate is reduced using algorithms that search for clusters of hits. Only the cluster data along with trigger information of the event are transmitted to the CMS DAQ system using the SLINK-64 protocol at a maximum rate of 640 Mbytes/s. All data processing algorithms on the FED are executed in large on-board Field Programmable Gate Arrays (FPGA). Two FED cards have been manufactured during the last quarter of 2002. Results on the performance of the FED are presented and discussed. I