The Merger board of the CDF Silicon Vertex Tracker

The Merger board is part of the Silicon Vertex Tracker (SVT), a device dedicated to perform real-time track reconstruction with offline-like resolution and high efficiency at the Level 2 trigger of the CDF experiment. The Merger is a custom 9U /spl times/ 400 mm VME board, running at an internal clock frequency of 33 MHz. Its main functional task in SVT is to merge up to four independent data streams into a single one. The merging operation can be performed on a first come, first served basis or according to an ordered sequence. There are four input streams and two identical output streams, so that the Merger also serves as a data fanout function. The board implements detailed error handling and sophisticated data monitoring that make it possible to trace back misfunctioning both in the Merger and in other parts of SVT. Furthermore, the Merger has special modes of operation that can be selected for test and diagnostic purposes. In these working modes, the Merger is a powerful tool that allows one to test other SVT boards at their maximum operating frequency.