Upgrade of the EAST central Timing System

EAST Distributed Synchronization and Timing System (DSTS) provides trigger and clock signals for control and measurement. Base on the embedded technology and the field programmable gate arrays (FPGA), a DSTS is designed in distributed structure, which is composed of one Core Module Unit (CMU), some Local Synchronized Node Units (LSNU), some auxiliary hardware interface, an optical network and a managing program. The upgrade is focused on the LSNU and some philosophies are adopted in the design of the DSTS. The upgraded DSTS system has many new functions, simplifies signals connection and reduces instrument size. It is a highly integrated system, with more reliability, flexibility and lower power consumption. The new DSTS has already been used in the 2009 EAST experimental campaign.