Design And Implementation Of Clock System For Industrial Ethernet Switch

With the gradual increase of data transmission rate of communication network,high reliability and high stability become the measure of information transmission and information exchange ability.In the network of data exchange and transmission,the clock oscillation unit is one of the most basic and important components of each system,and it is also one of the basic reasons for the stability and reliability of data transmission.In the network transmission system,the reference clock of the system at all levels maintain the frequency and precision in a certain range,to ensure that information in the cascade system the accuracy of collection.Synchronous communication network system needs to adjust the system clock distributed everywhere,and realizes the synchronization of each system unit in the network in accordance with a unified standard synchronization.In this thesis,based on the high reliability and high stability requirements of the communication network transmission,the phenomena that Ethernet switch is prone to transmission packet loss and the problem of synchronization lock 1PPS clock losing lock in the process of application industrial environmental temperature changes are researched.In this paper,two factors that affect the stability of the clock signal: clock source frequency accuracy and frequency stability,the signal integrity of clock design topology are researched and analyzed.And then the requirements of the clock performance of the switching unit in the Industrial Ethernet switch and the reasons for the packet loss caused by the switching unit are explored;The requirements of the clock source for the Industrial Ethernet switch synchronous clock unit,effect of the local oscillator clock on the performance of the lock 1PPS,and the cause of the 1PPS loss are studied.Clock oscillation circuit from the traditional LC oscillation circuit to today's quartz crystal oscillator,because of the advantages of high frequency,high precision,high stability,it become the main choice for people to design the clock oscillation circuit.According to the classification and characteristics of existing quartz crystal oscillators,the application of TCXO and OCXO in synchronous network is studied.Finally,the design principle of clock source,local oscillator clock and oscillation IC,the method of improving the frequency accuracy and temperature stability of crystal oscillator,and the crystal oscillator selection and design strategy suitable for industrial environment are studied.The effects of crystal AT cutting and SC cutting on the performance of the clock source are analyzed,and the clock synchronization chip is used for clock management and synchronization time design.The frequency stability of the switching unit reference clock in the industrial environment,and the high stability of the phase locked loop clock in the synchronization unit are improve.Through the study of the reliability of the switching clock system and the synchronous clock system,a clock unit reliability design of the PTP Industrial Ethernet switch was completed,the reliable transmission performance of Industrial Ethernet switch in network node and the accurate time synchronization performance have been improved.According to the test of clock accuracy,clock stability,clock synchronization performance and system transmission performance,the highly stable and highly reliable clock performance of PTP Industrial Ethernet switches are verified.The design meets the requirements of the RS-P328 I product system,realizes the RSP328 I PTP Industrial Ethernet switch to transmit zero packet loss and precision time synchronization.And it passed the testing standard for electrical equipment testing of China Electric Power Research Institute.