A SHARC DSP cluster as HERA-B DAQ building block

The CP violation experiment HERA-B at DESY requires highly selective on-line filtering of data due to high interaction rates and low signal to background ratio. This demands a hierarchical trigger system and data acquisition with high bandwidth. A complete level of the trigger hierarchy and the DAQ chain can be built from a single unit type: a single slot 6U VME unit carrying six ADSP21060 (SHARC) DSPs. The six SHARCs communicate via the common bus or via their link ports, which are all accessible from the front panel. Up to 350 units will be used in the experiment. Prototype units have been built and are operating successfully.