  In high energy physics experiment trigger systems, track segment seeding is a
resource consuming function and the primary reason is the computing complexity
of the segment finding process. As the Moore's Law is reaching its physical
limit, reducing computing complexity should be carefully considered, rather
than keep piling up silicon resources. The Tiny Triplet Finder is a scheme that
reduces the computing complexity of the segment seeding. As a proof of concept,
a 3D track segment seeding engine core based on the Tiny Triplet Finder has
been implemented and tested in a low-cost FPGA device. The seeding engine is
designed to preselect and group hits (stubs) from detector layers to feed
subsequent track fitting stage. The seeding engine consists of a Hough
transform space for r-z view and a Tiny Triplet Finder for r-phi view to
implement 3D constraints. The seeding engine is organized as a pipeline so that
each hit is processed in a single clock cycle. Taking advantage of the
register-like storage block scheme which enables effectively resetting of a
block RAM within a single clock cycle, clearing or refreshing the seeding
engine takes only one clock cycles between two events. The Tiny Triplet Finder
is also a generic coincidence finding scheme that can be used for many tasks.
As a versatility demonstration, track segment finding performances for two
distinctive detector geometries are tested in our seeding engine. In a collider
barrel-layer geometry, the fake segment rates are studied for 3D (i.e., both
r-phi and r-z views) and 2D (i.e., r-phi or r-z view only) configurations for
high hit multiplicity events (>4000 hits/layer in the barrel region). Another
detector geometry contains strip plane layers with timing information. The
numbers of coincidences, both real or fake, with or without timing ("3D" or
"2D") information at various hit multiplicities are studied.
