基于EPA协议的精确时钟同步方法  

Method for Precise Time Synchronization Based on EPA Protocol

作　　者：张艳[1] 韩雁[1] 霍明旭[1] 陈金龙[1] 廉玉平[1] 

机构地区：[1]浙江大学微电子与光电子研究所,杭州310027

出　　处：《传感技术学报》2009年第7期978-982,共5页Chinese Journal of Sensors and Actuators

摘　　要：工业以太网中通讯链路的不对称性,使得IEEE1588协议中的从时钟偏差计算方法并不适用。本文在EPA(Ether-net for Plant Automation)协议中CSME(Communication Scheduling Management Entity)算法调度的基础上分析了IEEE1588时间同步协议,提出了一种从时钟同步于主时钟的加权修正算法,同时应用晶振频率补偿算法,使得满足了基于EPA协议的工业以太网系统中同步数据采集和控制的实时性要求。采用硬件描述语言(Verilog HDL)和现场可编程逻辑门阵列(FPGA)实现了这种硬件时钟同步方法。该方法解决了传统的基于片上系统(SOC)时钟同步方案中时间戳不稳定、同步精度低等问题。使用Xilinx Spartan3 XC3S1500的FPGA验证了主从时钟的一致性,160ns的标准偏差和50ns的时间偏差平均值的测试结果证明了本文中算法较之协议中原算法的优越性。该方法也为集成现有网卡芯片的系统提供了一种高性价比和高精度的时钟同步解决方案。The asymmetry of communication path in industrial ethernet makes the offset adjusting algorithm inaccurate. Improved algorithms in offset adjusting and frequency compensation based on the CSME （Communication Scheduling Management Entity）scheduling of EPA （Ethernet for Plant Automation）protocol are proposed, which lead to deterministic and real-time communication in industrial ethernet control systern. The solutions are implemented by Verilog Hardware Description Language （Verilog HDL）and evaluated on field-programmable gate array （FPGA）of Xilinx Spartans3 XC3S1500. Problems such as uncertain time delay of timestamp and low time accuracy are solved. The performance results with Std. Dev（standard deviation）of 160ns and the mean of 50ns confirm the feasibility of the proposed algorithms in offset adjusting and frequency compensation. The solution is high cost performance compared with traditional time synchronization method for the SOC（System On Chip）system which can take advantage of the net interface card.

关 键 词：EPA IEEE1588 工业以太网 精确时钟同步 现场可编程逻辑门阵列 

分 类 号：TN919[电子电信—通信与信息系统] TN47[电子电信—信息与通信工程]