Altera cyclone V Technical Reference page 1262

cv_5v4
2016.10.28
Figure 17-13: Networked Time Synchronization
Master Clock TIme
t
1
t
2m
t
3m
t
4
The PTP uses the following process for synchronizing a slave node to a master node by exchanging the
PTP messages:
1. The master broadcasts the PTP Sync messages to all its nodes. The Sync message contains the master's
reference time information. The time at which this message leaves the master's system is t1. This time
must be captured, for Ethernet ports, at the PHY interface.
2. The slave receives the sync message and also captures the exact time, t2, using its timing reference.
3. The master sends a follow_up message to the slave, which contains t1 information for later use.
4. The slave sends a delay_req message to the master, noting the exact time, t3, at which this frame leaves
the PHY interface.
5. The master receives the message, capturing the exact time, t4, at which it enters its system.
6. The master sends the t4 information to the slave in the delay_resp message.
7. The slave uses the four values of t1, t2, t3, and t4 to synchronize its local timing reference to the
master's timing reference.
Most of the PTP implementation is done in the software above the UDP layer. However, the hardware
support is required to capture the exact time when specific PTP packets enter or leave the Ethernet port at
Ethernet Media Access Controller
Send Feedback
Sync Message
Delay_Req
Message
Delay_Resp Message
Containing t
Time
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Follow_Up Message
Containing t Value
1
Value
4
†
IEEE 1588-2002 Timestamps
Slave Clock Time
Data at
Slave Clock
t
t
2
2
t , t
1 2
t t , t , t
3 1 2 3
t , t , t , t
1 2 3 4
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17-47
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