The TOF trigger sub-system on the upgrading Beijing Spectrometer is designed to receive 368 bits fast hit signals from the front end electronics module to yield 7 bits trigger information according to the physical requirement.It sends the processed real time trigger information to the Global-Trigger-Logic to generate the primal trigger signal L1

and sends processed 136 bits real time position information to the Track-Match-Logic to calculate the particle flight tracks.The sub-system also packages the valid events for the DAQ system to read out.Following the reconfigurable concept

a large number of programmable logic devices are employed to increase the flexibility and reliability of the system

and decrease the complexity and the space requirement of PCB layout.This paper describes the implementation of the kernel trigger logic in a programmable logic device.