HESG447224R2工控卡件
可以检查该值以确定从网络接收的分组是否具有新的数据样本，或者它是否是先前接收的相同数据。PLC CPU可以通过三种方式从时间时钟源获取时间戳，具体取决于PLC配置：1。PLC CPU可以通过与以太网接口的时钟（与CPU中的时钟或网络上的外部SNTP服务器同步）同步来获得时间戳。2.PLC CPU可以通过与具有嵌入式以太网接口的CPU同步来获得时间戳。嵌入式以太网的内部时钟可以与网络上的外部SNTP服务器同步。3.当TOD时钟与SNTP服务器同步时，可以从CPU的TOD时钟获得时间戳数据。考虑到可编程逻辑控制器的不同配置方式，下表显示了EGD时间戳将如何受到每个可用AUP的影响。SNTP CPU TOD时钟同步UTC偏移DST时间CPE生成的EGD交换已禁用-启用启用的CPU时钟在以太网接口中受影响。CPU仅将此时间戳用于以太网全局数据交换。以太网接口的时间戳不会影响CPU内部时钟的时间。7.4.1.1以太网接口时钟如果CPU和ETM之间的时间同步丢失（例如，在电源循环或停止运行转换期间），CPU使用自己的时钟作为时间戳。CPU以太网接口CPU时间时钟时间戳时间戳EGD带时间戳图45：从以太网接口时钟获取时间戳以太网接口中的时间时钟与CPU中的时钟或网络上的外部SNTP服务器同步。以太网全局数据时间戳源的选择是以太网接口基本配置的一部分，如第4章所述。PAC系统™ RX3i和RSTi EP TCP/IP以太网通信用户手册第7节GFK-2224Y 2019年8月SNTP操作131 7.4.1.2 PLC的时钟如果选择此源，以太网接口的内置时钟在通电或重启时与PLC CPU中的时钟同步。PLC产生的时间戳信息具有100微秒的分辨率。由于网络上PLC中的时钟不同步，不同PLC产生的EGD时间戳无法准确比较。CPU以太网接口时钟时间戳CPU时间CPU时钟图46：从PLC时钟获取时间戳7.4.1.3 SNTP服务器的时钟如果选择此源，以太网接口的内置时钟将定期与网络上SNTP服务器上的时钟同步。所有配置为使用SNTP的以太网接口将具有更新的同步时间戳。因此，可以在交换的数据之间进行精确的定时比较。如果SNTP用于执行网络时间同步，则时间戳信息通常在同一网络上的PLC之间具有±10毫秒的精度。PAC系统™ RX3i和RSTi EP TCP/IP以太网通信用户手册第7节GFK-2224Y 2019年8月SNTP操作132 CPU以太网接口SNTP时间CPU时钟SNTP时间服务器网络时间戳EGD和时间戳时钟图47：从SNTP服务器的时钟获取时间戳7.4.2从CPU TOD时钟获取时间戳记将CPU TOD同步到SNTP服务器允许您跨多个系统设置一致的时间。一旦CPU TOD时钟与ETM上的SNTP时间同步，所有生成的EGD交换机将使用CPU的TOD作为时间戳。7.4.2.1将CPU TOD时钟同步到SNTP服务器用户可以使用以下两种方法之一将CPU TOD时钟同步到SNATP服务器：1。在PME中配置硬件配置的以太网设置
This value can be examined to determine whether a packet received from the network has a new data sample or if it is the same data received previously. There are three ways a PLC CPU can acquire a timestamp from a time clock source depending on the PLC configuration: 1. The PLC CPU can obtain a timestamp by synchronizing with the Ethernet interface’s time clock (which is synchronized with either the clock in the CPU or an external SNTP server on the network). 2. The PLC CPU can obtain a timestamp by synchronizing with a CPU with an embedded ethernet interface. The embedded Ethernet’s internal time clock can be synchronized with an external SNTP server on the network. 3. The timestamp data can be obtained from the CPU’s TOD clock when the TOD clock is synchronized with an SNTP server. Given the number of different ways that a PLC can be configured, the chart below demonstrates how the EGD Timestamps will be affected by each of the AUPs available. SNTP CPU TOD Clock Sync UTC Offset DST Time CPE Produced EGD Exchanges Disabled - Enabled Enabled CPU Clock Affected in the Ethernet interface. The CPU only uses this timestamp for Ethernet Global Data exchanges. The timestamp from the Ethernet interface does not affect the time of the CPU's internal time clock. 7.4.1.1 Ethernet Interface Clock If time synchronization between the CPU and ETM is lost (for example, during power cycle or stop-to-run transition) the CPU uses its own clock for the time stamp. CPU Ethernet interface CPU time clock timestamp time clock EGD with timestamp Figure 45: Obtaining Timestamps from the Ethernet interface Clock The time clock in the Ethernet interface is synchronized to either the clock in the CPU or an external SNTP server on the network. Selection of the timestamp source for Ethernet Global Data is part of the basic configuration of the Ethernet interface, as explained in Chapter 4. PACSystems™ RX3i and RSTi-EP TCP/IP Ethernet Communications User Manual Section 7 GFK-2224Y August 2019 SNTP Operation 131 7.4.1.2 PLC's Time Clock If this source is selected, the Ethernet interface’s built-in time clock is synchronized at power-up or at restart to the clock in the PLC CPU. The timestamp information produced by the PLC has a resolution of 100 microseconds. Because the time clocks in the PLCs on the network are not synchronized, EGD timestamps produced by different PLCs cannot be compared accurately. CPU Ethernet interface time clock timestamp CPU Time CPU time clock Figure 46: Obtaining Timestamps from the PLC Time Clock 7.4.1.3 SNTP Server's Time Clock If this source is selected, the Ethernet interface’s built-in clock is periodically synchronized to the clock on an SNTP server on the network. All Ethernet interfaces configured to use SNTP will have updated, synchronized timestamps. Therefore, accurate timing comparisons between exchanged data can be made. If SNTP is used to perform network time synchronization, the timestamp information typically has ±10 millisecond accuracy between PLCs on the same network. PACSystems™ RX3i and RSTi-EP TCP/IP Ethernet Communications User Manual Section 7 GFK-2224Y August 2019 SNTP Operation 132 CPU Ethernet interface SNTP Time CPU time clock SNTP Time Server on Network timestamp EGD with timestamp time clock Figure 47: Obtaining Timestamps from the SNTP Server’s Time Clock 7.4.2 Obtaining Timestamps from the CPU TOD Clock Synchronizing the CPU TOD clock to an SNTP server allows you to set a consistent time across multiple systems. Once the CPU TOD clock is synchronized with the SNTP time on an ETM, all produced EGD exchanges will use the CPU’s TOD for the time stamp.21 The CPU TOD clock is set with accuracy within ±2ms of the SNTP time stamp. 7.4.2.1 Synchronizing the CPU TOD Clock to an SNTP Server The user can synchronize the CPU TOD Clock to an SNTP server using one of two methods: 1. Configuring the Hardware Configuration’s Ethernet settings in PME
