Altera cyclone V Technical Reference page 1268

cv_5v4
2016.10.28
Ordinary Clock
The ordinary clock in a domain supports a single copy of the protocol. The ordinary clock has a single PTP
state and a single physical port. In typical industrial automation applications, an ordinary clock is
associated with an application device such as a sensor or an actuator. In telecom applications, the ordinary
clock can be associated with a timing demarcation device.
The ordinary clock can be a grandmaster or a slave clock. It supports the following features:
• Sends and receives PTP messages. The timestamp snapshot can be controlled as described in the
Timestamp_Control
• Maintains the data sets such as timestamp values.
The table below shows the messages for which you can take the timestamp snapshot on the receive side for
Master and slave nodes. For an ordinary clock, you can take the snapshot of either of the following PTP
message types: version 1 or version 2. You cannot take the snapshots for both PTP message types. You can
take the snapshot by setting the control bit (
Timestamp_Control
Table 17-19: Ordinary Clock: PTP Messages for Snapshot
Delay_Req
Boundary Clock
The boundary clock typically has several physical ports communicating with the network. The messages
related to synchronization, master-slave hierarchy, and signaling terminate in the protocol engine of the
boundary clock and are not forwarded. The PTP message type status given by the MAC helps you to
identify the type of message and take appropriate action. The boundary clock is similar to the ordinary
clock except for the following features:
• The clock data sets are common to all ports of the boundary clock .
• The local clock is common to all ports of the boundary clock. Therefore, the features of the ordinary
clock are also applicable to the boundary clock.
End-to-End Transparent Clock
The end-to-end transparent clock supports the end-to-end delay measurement mechanism between slave
clocks and the master clock. The end-to-end transparent clock forwards all messages like normal bridge,
router, or repeater. The residence time of a PTP packet is the time taken by the PTP packet from the ingess
port to the egress port.
The residence time of a SYNC packet inside the end-to-end transparent clock is updated in the correction
field of the associated Follow_Up PTP packet before it is transmitted. Similarly, the residence time of a
Delay_Req packet inside the end-to-end transparent clock is updated in the correction field of the
associated Delay_Resp PTP packet before it is transmitted. Therefore, the snapshot needs to be taken at
both ingress and egress ports only for PTP messages SYNC or Delay_req. You can take the snapshot by
setting the snapshot select bits (
The
snaptypsel
packet types for which a snapshot needs to be taken. The encoding is shown in the table below:
Ethernet Media Access Controller
Send Feedback
†
register.
†
register.
Master
†
snaptypesel
bits, along with bits 15 and 14 in the
†
†
) and selecting the snapshot mode in the
tsver2ena
†
†
†
) to b'10 in the
Timestamp_Control
Timestamp Control
Ordinary Clock
†
Slave
SYNC
†
†
register.
register, decide the set of PTP
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†