High Resolution Time Synchronization over SpaceWire Links

In this paper, an extension to the SpaceWire standard (Parkes et al., 2003) is presented which increases considerably its synchronization capability. Initially developed in the scope of Simbol-X (Ferrando et al., 2006), a CNES formation flying instrument where time-tagging of data science from three detectors is critical to perform on-board processing, the extension can be implemented in all equipments where the use of the performing spacewire standard is not possible due to its intrinsic synchronization limitation. This limitation gives a lack of precision ten times the data transmission period rate plus two periods of the receiver synchronization clock. With the additional feature this uncertainty is reduced to two periods of the receiver synchronization clock. The extension takes advantage of already existing capabilities of the spacewire standard with no impact on the data layer and very limited additional resource needs. The resulting performances measured on a prototype are presented still in the framework of the Simbol-X instrument using ACTEL space qualified FPGA as target.