  The architecture of the ZEUS Micro Vertex Detector data acquisition system
and the implementation of its second level trigger, the ZEUS Global Track
Trigger are described. Data from the vertex detectors HELIX read-out chips,
corresponding to 200k channels, are digitized by 3 crates of ADCs which perform
noise and pedestal subtraction, and data suppression and compaction. PowerPC
VME board computers push cluster data for second level trigger processing and
strip data for event building via Fast and Gigabit Ethernet network
connections. Additional tracking information from the central tracking chamber
and the forward straw tube tracker are interfaced into the 12 dual CPU PC farm
of the Global Track Trigger where track and vertex finding is performed. The
system is data driven at the ZEUS first level trigger rate (~500Hz) and must
generate a trigger result after a mean time of 10ms.
