R31DS0087EU0101 Rev.1.01

Page 5

Sep.28.21

pcm4l Datasheet

1. Principles of Operation

The IEEE 1588-2019 Precision Time Protocol (PTP) can be used to achieve precise synchronization of clocks in

packet-based networked systems. The protocol supports synchronization accuracy and precision in the sub-

microsecond range with minimal network and local computing resources, and allows for customizations by means

of Profiles. With a properly designed network, sub-nanosecond time transfer accuracy can be achieved.

The challenge of any network synchronization mechanism is how to make local clocks that are traceable to a

primary clock source. It is also desirable to implement a clear set of equipment clock recommendations. For

Telecom, these industry agreed architectures come from the ITU-T.

1.1 Simplified Synchronization Model

The basis of PTP is built on the exchange of PTP timing messages, as illustrated in Figure 1. The IEEE 1588

standard defines two types of delay mechanisms: delay request-response and peer delay. Only one of the two is

needed, and all ITU-T Telecom Profiles use the delay request-response. PTP assumes transmission delays

between the master clock to the slave clock and the return path are symmetric.

Figure 1. Basic PTP Timing Message Exchange (from IEEE 1588-2019)

From above, two measurements can be obtained:

1. Offset From Master, or <offsetFromMaster>

◦ = <Time on the Slave Clock> - <Time on the Master Clock>

◦ = <syncEventIngressTimestamp> - <originTimestamp> - <meanDelay> - <correctedSyncCorrectionField>

◦ = t2 - t1 - <meanPathDelay>[1] - <correctedSyncCorrectionField>

1. Using delay request-response mechanism (used by all ITU-T Telecom Profiles).