The design of a processor to trigger on long-lived particles (e.g. b-quarks) for the DØ experiment at the Fermilab Tevatron is presented. This device reconstructs the trajectory of the charged particles in the DØ tracking system, which consists of a central fiber tracker and a silicon microstrip tracker. The r- φ impact parameter resolution of the fitted tracks is about 40 μm. This enables the identification of the long-lived b-quarks produced in the decays of various particles, e.g. the top quarks, Higgs Boson, techni-particles and other exotic particles produced in pp¯ collisions at the Tevatron. In this report we describe the design of the architecture and algorithms for the Silicon Track Trigger.