A data transmission method for particle physics experiments based on Ethernet physical layer  

作　　者：黄锡汝 曹平 郑佳俊 

机构地区：[1]State Key Laboratory of Particle Detection and Electronics, University of Science and Technology of China [2]Anhui Key Laboratory of Physical Electronics, Department of Modern Physics, University of Science and Technology of China

出　　处：《Chinese Physics C》2015年第11期65-69,共5页中国物理C（英文版）

基　　金：Supported by National Natural Science Foundation of China(11005107);Independent Projects of State Key Laboratory of Particle Detection and Electronics(201301)

摘　　要：Due to its advantages of universality, flexibility and high performance, fast Ethernet is widely used in readout system design for modern particle physics experiments. However, Ethernet is usually used together with the TCP/IP protocol stack, which makes it difficult to implement readout systems because designers have to use the operating system to process this protocol. Furthermore, TCP/IP degrades the transmission efficiency and real-time performance. To maximize the performance of Ethernet in physics experiment applications, a data readout method based on the physical layer（PHY） is proposed. In this method, TCP/IP is replaced with a customized and simple protocol, which makes it easier to implement. On each readout module, data from the front-end electronics is first fed into an FPGA for protocol processing and then sent out to a PHY chip controlled by this FPGA for transmission.This kind of data path is fully implemented by hardware. From the side of the data acquisition system（DAQ）,however, the absence of a standard protocol causes problems for the network related applications. To solve this problem, in the operating system kernel space, data received by the network interface card is redirected from the traditional flow to a specified memory space by a customized program. This memory space can easily be accessed by applications in user space. For the purpose of verification, a prototype system has been designed and implemented.Preliminary test results show that this method can meet the requirements of data transmission from the readout module to the DAQ with an efficient and simple manner.Due to its advantages of universality, flexibility and high performance, fast Ethernet is widely used in readout system design for modern particle physics experiments. However, Ethernet is usually used together with the TCP/IP protocol stack, which makes it difficult to implement readout systems because designers have to use the operating system to process this protocol. Furthermore, TCP/IP degrades the transmission efficiency and real-time performance. To maximize the performance of Ethernet in physics experiment applications, a data readout method based on the physical layer（PHY） is proposed. In this method, TCP/IP is replaced with a customized and simple protocol, which makes it easier to implement. On each readout module, data from the front-end electronics is first fed into an FPGA for protocol processing and then sent out to a PHY chip controlled by this FPGA for transmission.This kind of data path is fully implemented by hardware. From the side of the data acquisition system（DAQ）,however, the absence of a standard protocol causes problems for the network related applications. To solve this problem, in the operating system kernel space, data received by the network interface card is redirected from the traditional flow to a specified memory space by a customized program. This memory space can easily be accessed by applications in user space. For the purpose of verification, a prototype system has been designed and implemented.Preliminary test results show that this method can meet the requirements of data transmission from the readout module to the DAQ with an efficient and simple manner.

关 键 词：readout method ETHERNET physical layer data redirection 

分 类 号：TP393.11[自动化与计算机技术—计算机应用技术] O572.21[自动化与计算机技术—计算机科学与技术]