UM10503
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User manual
Rev. 1.3 — 6 July 2012
731 of 1269
NXP Semiconductors
UM10503
Chapter 26: LPC43xx Ethernet
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 the messages mentioned in
You can take the snapshot by setting the snapshot select bits (SNAPTYPSEL) to 10 in
26.7.4.2.4
Peer-to-peer transparent clock support
In this type of clock the computation of the link delay is based on an exchange of
Pdelay_Req, Pdelay_Resp and Pdelay_Resp_Follow_Up messages with the link peer.
Hence support for taking snapshot for the event messages related to Pdelay is added.
The transparent clock corrects only the SYNC and Follow-up message. As discussed
earlier this can be achieved using the message status provided.
The type of clock to be implemented will be configurable through control register (see
). To ensure that the snapshot is taken only for the messages indicated in the
table for the corresponding clock type, the .TSEVNTENA: Enable Time Stamp Snapshot
for Event Messages. bit has to be set.
26.7.4.3 PTP processing and control
Table 4-5 shows the common message header for the PTP messages. This format is
taken from IEEE standard 1588-2008 (Revision of IEEE Std. 1588-2002).
Table 578. End-to-end transparent clock: PTP messages for which a snapshot is taken for
transparent clock implementation
SYNC
FOLLOW_UP
Table 579. End-to-end transparent clock: PTP messages for which a snapshot is taken for
transparent clock implementation
SYNC
Pdelay_Req
Pdelay_Resp
Table 580. Message format defined in IEEE 1588-2008
Bits
7
6
5
4
3
2
1
0
OCTETS
OFFSET
transportSpecific messageType
1
0
Reserved versionPTP
1
1
messageLength 2
2
domainNumber 1
4
Reserved 1
5
flagField 2
6
correctionField 8
8
Reserved 4
16
sourcePortIdentity 10
20
