LAN9353 Datasheet, PDF (396/523 Pages) Microchip Technology – Interfaces at up to 200Mbps via Turbo MII

LAN9353
15.2 PTP Timestamp and Residence Time Correction
This sub-module handles all PTP packet tasks related to recording timestamps of packets, accounting for the frame for-
warding delay through the switch and inserting timestamps into packets.
Modes supported are:
• Boundary Clock, master and slave, one-step and two-step, end-to-end or peer-to-peer delay
- All 1588 packets are to and from the Host MAC (as directed by switch core)
- Special Host VLAN tagging (via switch core) indicates ingress port and desired egress port
- RX and TX timestamps saved in registers for S/W
- RX timestamp stored in packet for ease of retrieval by S/W
- Egress timestamp of Sync packet inserted on-the-fly for one-step
- TX timestamp of Delay_Req packet stored in received Delay_Resp packet for ease of retrieval
- Correction Field and ingress timestamp of Pdelay_Req packet saved in registers for one-step turnaround time
- Correction Field of Pdelay_Resp packet automatically calculated and inserted on-the-fly for one-step
- PTP checksums and Ethernet FCS updated on-the-fly
- Ingress and egress timestamps corrected for latency
- Asymmetry corrections
- Peer delay correction on received Sync packets
• Transparent Clock with Ordinary Clock, master and slave, one-step and two-step, end-to-end or peer-to-peer
delay
- Peer-to-peer received 1588 packets forwarded to Host (peer-to-peer mode) or to other network port (end-to-
end mode) (as directed by switch core)
- All other received 1588 packets forwarded to Host and other network port (as directed by switch core)
- Special Host VLAN tagging (via switch core) indicates ingress port and desired egress port
- RX and TX timestamps saved in registers for S/W
- RX timestamp stored in packet for ease of retrieval by S/W
- Residence time correction on forwarded Sync, Delay_Req, Pdelay_Req and Pdelay_Resp packets
ingress timestamp subtracted from Correction Field on receive
egress timestamp added to Correction Field on-the-fly during transmit
- Egress timestamp of Host Sync packet inserted on-the-fly for one-step (for master Ordinary Clock)
- Correction Field and ingress timestamp of Pdelay_Req packet saved in registers for one-step turnaround time
(peer-to-peer mode)
- Correction Field of Host Pdelay_Resp packet automatically calculated and inserted on-the-fly for one-step
(peer-to-peer mode)
- PTP checksums and Ethernet FCS updated on-the-fly
- Ingress and egress timestamps corrected for latency
- Asymmetry corrections
- Peer delay correction on received Sync packets
Functions include:
• Detecting a PTP packet
- 802.3/SNAP or Ethernet II encoding
- Skipping over VLAN tags
- Ethernet, IPv4 or IPv6 message formats
- Skipping over IP extension headers
- Checking the MAC and / or the IP addresses
• Recording the timestamp of received packets into registers
- Accounting for the ingress latency
• Recording the timestamp of received packets into the packet and updating the layer 3 checksum and layer 2 FCS
fields
- Accounting for the ingress latency
DS00001925A-page 396
 2015 Microchip Technology Inc.