The full name is "Precision Clock Synchronization Protocol Standard for Network Measurement and Control System", which is a time synchronization protocol for measurement and control systems based on industrial Ethernet. IEEE1588 protocol is a general specification to improve the timing synchronization capability of network systems. It is mainly prepared with reference to Ethernet in the drafting process, so that distributed communication networks can have strict timing synchronization and be applied to industrial automation systems. The IEEE 1588 standard has two versions: version 1 and version 2.
Brief introduction to clock synchronization
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PTP clock synchronization includes frequency synchronization and time synchronization. In simple terms, frequency synchronization is to adjust the time speed of the master and slave clocks. As long as the frequency between them is the same, regardless of the time phase, as long as the local clock signal is adjusted to have the same frequency as the clock source, the signal appears at the same rate at the same instant. Time synchronization is to make the master and slave clocks have the same time reference and the same time. Time synchronization means that not only the frequency but also the phase should be synchronized between master and slave clocks.
In many applications, data acquisition needs to be carried out synchronously across the network, such as bridge condition monitoring, dam monitoring, static test of aircraft, and dynamic mechanics test of aircraft. Because there are many acquisition points, ranging from thousands to tens of thousands of points, and the acquisition speed ranges from tens of Hertz to hundreds of Hertz, these applications unify high-precision clocks through large-scale clock board card systems.
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PTP clock processing mode
PTP clock synchronization modes can be divided into two steps (also called two-step or two-step mode) and one step (one-step or one-step mode), both of which require software protocol processing and hardware chip support.
The comparison of one step and two step message marks is shown in the figure below:
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When two-step is selected, marking the time stamp of sending message is completed by two-step message. For example, the master clock sends the time stamp t1 generated by the Sync synchronization message. When sending, the hardware chip marks it and places it in the software fifo list. When setting up the followUp message to send, it will take the time stamp t1 and place it in its own message time stamp field to send it to the slave clock for synchronization.
When one step mode is selected, the master clock sends the message to be marked directly. For example, when the master clock sends the Sync message, the hardware chip marks t1 and places it in the time stamp field of the Sync message to send it directly. It does not need followUp to send it. One step fast processing requires hardware support, and the time lost in processing can be ignored.
Main applications of PTP
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Application of PTP in Railway/Highway/Bridge Condition Monitoring
The bridge condition monitoring system is essentially a synchronous data acquisition and analysis system. For example, when the stress calculation is measured at both ends of the bridge, the clocks of the data acquisition systems at both ends must be synchronized with high accuracy. High precision synchronization is more necessary for nondestructive testing system and signal system of railway lines.
Application of PTP in Billing
At present, billing service automation is widely used, such as telephone billing, broadband/narrowband online billing, intelligent network service billing, and grid billing. These business platform billing systems all need accurate and stable clock synchronization. Supporting IEEE1588 (PTP) switches is very suitable for large-scale deployment in these application network systems.
Application of PTP in Signaling System
The communication between any two communication terminals in the communication network cannot be separated from signaling, and the signaling must be correctly executed to ensure normal communication between end users. IEEE1588 (PTP) is very suitable for meeting such application requirements.
Application of PTP in Wireless base Station
Different systems of wireless technology have different requirements for clock carrying. Therefore, if the wireless base station wants to provide accurate positioning service, it must ensure that the devices between the base stations maintain high-precision synchronization at the submicron level.
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