  The Large Area Water Cherenkov Array (LAWCA) experiment focuses on high
energy gamma astronomy between 100 GeV and 30 TeV. Invoked by the idea of
hardware triggerless structure, a prototype of LAWCA trigger electronics is
implemented in one single VME-9U module which obtains all the data from the 100
Front End Electronic (FEE) endpoints. Since the trigger electronics accumulates
all the information, the flexibility of trigger processing can be improved.
Meanwhile, the dedicated hardware trigger signals which are fed back to front
end are eliminated; this leads to a system with better simplicity and
stability. To accommodate the 5.4 Gbps system average data rate, the fiber
based high speed serial data transmission is adopted. Based on the logic design
in one single FPGA device, real-time trigger processing is achieved; the
reprogrammable feature of the FPGA device renders a reconfigurable structure of
trigger electronics. Simulation and initial testing results indicate that the
trigger electronics prototype functions well.
