The Advanced Photon Source Event System*

F. Lenkszus and R. Laird
Argonne National Laboratory


The Advanced Photon Source, like many other facilities, requires a means of transmitting timing information to distributed control system I/O controllers. The APS event system provides the means of distributing medium resolution/accuracy timing events throughout the facility. It consists of VME event generators and event receivers which are interconnected with100 Mbaud fiber optic links at distances of up to 650 m in either a star or point-to-point configuration. The systems event throughput rate is10 Mevents/sec with a peak-to-peak timing jitter down to 100ns depending on the source of the event. It is integrated into the EPICS- based APS control system through record and device support. Event generators broadcast timing events over fiber optic links to event receivers which are programmed to decode specific events. Event generators generate events in response to external inputs, from internal programmable event sequence rams, and from VME bus writes. The event receivers can be programmed to generate outputs, both pulse and set/reset level, to synchronize hardware and to generate interrupts to initiate EPICS record processing. In addition, each event receiver contains a time stamp counter which is used to provide synchronized time stamps to EPICS records.