SpaceWire光纤总线时钟同步方法研究
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摘要
将SpaceWire ECSS-E-50-12C标准中基于Time-Code时间分发的同步方式应用于SpaceWire光纤总线系统中时,存在计时精度不高且计时长度短、延时误差不可控、频率偏差无法补偿的问题,不能满足纳秒级的时钟同步需求。针对以上问题,提出了使用从节点的本地时钟计数、时间戳计算平均延时、以及根据时钟频率偏差调整动态时钟计数的方法,消除时钟同步过程中时钟延时、抖动和频率漂移的影响,提高时钟同步精度。通过仿真验证,在光纤总线系统主节点和从节点的时钟频率不同,传输延时为80ns,延时抖动为8ns,且同步间隙为100μs的情况下,优化后的时钟同步精度达到了从100μs到24ns的提升。
The use of time-code distribution based on SpaceWire ECSS-E-50-12 C standard in SpaceWire fiber-optic bus system exits some problems like low clock precision,uncontrollable latency and uncorrectable clock frequency deviation that can not meet the nanosecond clock synchronization requirements. In view of the above problems,this paper proposes a method of counting the local clock at the node,calculating average clock latency with time stamps and compensating the clock frequency deviation dynamically based on clock counting. Eliminate the effect of clock latency and clock frequency drift during the clock synchronization to improve the clock synchronization accuracy. Through the simulation test,the clock synchronization precision is improved from 100μs to 24 ns in the fiber-optic bus system when the transmission delay is 80 ns,the jitter is 8 ns,the resynchronization interval is 100μs and the master node and slave node have different clock frequency.
The use of time-code distribution based on SpaceWire ECSS-E-50-12 C standard in SpaceWire fiber-optic bus system exits some problems like low clock precision,uncontrollable latency and uncorrectable clock frequency deviation that can not meet the nanosecond clock synchronization requirements. In view of the above problems,this paper proposes a method of counting the local clock at the node,calculating average clock latency with time stamps and compensating the clock frequency deviation dynamically based on clock counting. Eliminate the effect of clock latency and clock frequency drift during the clock synchronization to improve the clock synchronization accuracy. Through the simulation test,the clock synchronization precision is improved from 100μs to 24 ns in the fiber-optic bus system when the transmission delay is 80 ns,the jitter is 8 ns,the resynchronization interval is 100μs and the master node and slave node have different clock frequency.
引文
[1]黄文君,遇彬.基于FPGA的精确时钟同步方法[J].浙江大学学报,2007(10):1697-1700.(Huang Wenjun,Yu Bin. Method for Precise Time Synchronization Based on FPGA[J]. Journal of Zhejiang University,2007(10):1697-1700.)
[2] Kopetz H. Real-time Systems:Design Principles for Distributed Embedded Applications[M]. Springer Science&Business Media,2011.
[3] Yin Hongtao,Fu P,Qiao J,et al. The Implementation of IEEE 1588 Clock Synchronization Protocol Based on FPGA[C]. 2018 IEEE International Instrumentation and Measurement Technology Conference(I2MTC). IEEE,2018:1-6.
[4] Steve Parkes. Space Wire User's Guide[M]. UK. 2012.
[5] Steve Parkes,Albert Ferrer Florit. Space Wire And SpaceFibre[M]. UK,2015.
[6]姜宏,杨孟飞,刘波,杨桦,龚健,吴军.高速Space Wire光纤总线系统研究与实现[C].全国工业控制计算机年会,2017,11:27-31.
[7]杨俊雄,徐亚军,何锋,等.时钟同步精度对TTE实时性影响研究[J].电光与控制,2016,23(8):33-38.(Yang Junxiong,Xu Yajun,He Feng,et al. Research on Influence of Clock Synchronization Accuracy to TTE Real Time Performance[J]. Electronics Optics&Control,2016,23(8):33-38.)
[2] Kopetz H. Real-time Systems:Design Principles for Distributed Embedded Applications[M]. Springer Science&Business Media,2011.
[3] Yin Hongtao,Fu P,Qiao J,et al. The Implementation of IEEE 1588 Clock Synchronization Protocol Based on FPGA[C]. 2018 IEEE International Instrumentation and Measurement Technology Conference(I2MTC). IEEE,2018:1-6.
[4] Steve Parkes. Space Wire User's Guide[M]. UK. 2012.
[5] Steve Parkes,Albert Ferrer Florit. Space Wire And SpaceFibre[M]. UK,2015.
[6]姜宏,杨孟飞,刘波,杨桦,龚健,吴军.高速Space Wire光纤总线系统研究与实现[C].全国工业控制计算机年会,2017,11:27-31.
[7]杨俊雄,徐亚军,何锋,等.时钟同步精度对TTE实时性影响研究[J].电光与控制,2016,23(8):33-38.(Yang Junxiong,Xu Yajun,He Feng,et al. Research on Influence of Clock Synchronization Accuracy to TTE Real Time Performance[J]. Electronics Optics&Control,2016,23(8):33-38.)