Performance and lessons of the CMS Global Calorimeter Trigger

The CMS Global Calorimeter Trigger (GCT) has been designed, manufactured and commissioned on a short time schedule of approximately two years. The GCT system has gone through extensive testing on the bench and in-situ and its performance is well understood. This paper describes problems encountered during the project, the solutions to them and possible lessons for future designs, particularly for high speed serial links. The input links have been upgraded from 1.6Gb/s synchronous links to 2.0Gb/s asynchronous links. The existing output links to the Global Trigger (GT) are being replaced. The design for a low latency, high speed serial interface between the GCT and GT, based upon a Xilinx Virtex 5 FPGA is presented.