Transmit datapath, Transmit datapath –24 – Altera 10-Gbps Ethernet MAC MegaCore Function User Manual
Page 91
7–24
Chapter 7: Functional Description
IEEE 1588v2
10-Gbps Ethernet MAC MegaCore Function User Guide
February 2014
Altera Corporation
7.9.2. 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 PTP packet when the client
specifies the Timestamp field offset and asserts Timestamp Insert Request.
■
Depending on the PTP device and message type, the MAC function updates
the residence time in the correction field of the PTP packet when the client
asserts
tx_etstamp_ins_ctrl_residence_time_update
and Correction Field
Update.The residence time is the difference between the egress and ingress
timestamps.
■
For PTP packets encapsulated using the UDP/IPv6 protocol, the MAC function
performs UDP checksum correction using extended bytes in the PTP packet.
■
The MAC function re-computes and re-inserts CRC-32 into the PTP packets
after each timestamp or correction field insertion.
■
The format of timestamp supported includes 1588v1 and 1588v2, (as specified
in Y.1731)
■
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
.
Table 7–4
summarizes the timestamp and correction field insertions for various PTP
messages in different PTP clocks.
Table 7–4. Timestamp and Correction Insertion for 1-Step Clock Synchronization
PTP Message
Ordinary Clock
Boundary Clock
E2E Transparent Clock
P2P Transparent Clock
Insert
Timestamp
Insert
Correction
Insert
Timestamp
Insert
Correction
Insert
Timestamp
Insert
Correction
Insert
Timestamp
Insert
Correction
Sync
Yes
(1)
No
Yes
(1)
No
No
Yes
No
Yes
Delay_Req
No
No
No
No
No
Yes
No
Yes
Pdelay_Req
No
No
No
No
No
Yes
No
No
Pdelay_Resp
No
Yes
(1)
,
No
Yes
(1)
,
No
Yes
No
Yes
(1)
,
Delay_Resp
No
No
No
No
No
No
No
No
Follow_Up
No
No
No
No
No
No
No
No
Pdelay_Resp_
Follow_Up
No
No
No
No
No
No
No
No
Announce
No
No
No
No
No
No
No
No
Signaling
No
No
No
No
No
No
No
No
Management
No
No
No
No
No
No
No
No
Notes to
Table 7–4
:
(1) Applicable only when 2-step flag in flagField of the PTP packet is 0.
(2) Applicable when you assert tx_etstamp_ins_ctrl_residence_time_update.