  Many physics topics to be studied by the D0 experiment during Run II of the
Fermilab Tevatron ppbar collider give rise to final states containing
b--flavored particles. Examples include Higgs searches, top quark production
and decay studies, and full reconstruction of B decays. The sensitivity to such
modes has been significantly enhanced by the installation of a silicon based
vertex detector as part of the DO detector upgrade for Run II. Interesting
events must be identified initially in 100-200 microseconds to be available for
later study. This paper describes custom electronics used in the DO trigger
system to provide the real--time identification of events having tracks
consistent with the decay of b--flavored particles.
