Altera Triple Speed Ethernet MegaCore Function - Manual (Page 73)

IEEE 1588v2 Architecture
Figure 4-26: Overview of the IEEE 1588v2 Feature
This figure shows only the datapaths related to the IEEE 1588v2 feature.
IEEE 1588v2
Tx Logic
IEEE 1588v2
Rx Logic
PTP Software
Stack
Time-of-Day
Clock
PHY
Tx
PHY
Rx
MAC PHY
tx_path_delay
rx_path_delay
Timestamp &
User Fingerprint
Correction
Time of Day
Timestamp Aligned to
Receive Frame
tx_egress_timestamp_request
tx_ingress_timestamp
tx_time_of_day
rx_time_of_day
IEEE 1588v2 Transmit Datapath
The IEEE 1588v2 feature supports 1-step and 2-step clock synchronizations on the transmit datapath.
• For 1-step clock synchronization:
• Timestamp insertion depends on the PTP device and message type.
• The MAC function inserts a timestamp in the Sync PTP message if the PTP clock operates as ordinary
or boundary clock.
• Depending on the PTP device and message type, the MAC function updates the residence time in the
correction field of the PTP frame when the client asserts
tx_etstamp_ins_ctrl_residence_time_update . The residence time is the difference between the
egress and ingress timestamps.
• For PTP frames encapsulated using the UDP/IPv6 protocol, the MAC function performs UDP
checksum correction using extended bytes in the PTP frame.
• The MAC function re-computes and re-inserts CRC-32 into the PTP frames after each timestamp or
correction field insertion.
• For 2-step clock synchronization, the MAC function returns the timestamp and the associated fingerprint
for all transmit frames when the client asserts
tx_egress_timestamp_request_valid
.
Altera Corporation Functional Description
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4-37 IEEE 1588v2 Architecture
UG-01008
2014.06.30