SSRF is a third generation,3.5GeV synchrotron light source currently being constructed in Shanghai.The conceptual consideration of its timing system is described in this paper.Different storage ring filling patterns such as single bunch pattern,multi-bunch filling pattern,mixed filling pattern and top-up pattern,demand a highly stable, low jitter timing system with the flexibility to recnfigure on programmable event driven basis.Based on the EPICS control system,the timing system provides digitally programmable sequencing and delay for the electron gun,the linac modulator,the booster and storage ring RF,the pulsed magnets,the instrumentation systems according to different operation pattern requirements.
