SNLS779A July 2025 – November 2025 DP83TC815-Q1
PRODUCTION DATA
The IEEE802.1AS PTP transmit parser monitors transmit packet data to detect IEEE802.1AS Event messages. The transmit parser can detect PTP Event messages transported directly in Layer2 Ethernet packets or PTP VLAN packets. Upon detection of a PTP Event Message, the device captures the transmit timestamp and provides the timestamp to host (MAC) for processing. In addition to PTP event based filtering, there is an option to filter and timestamp PTP event frames with a specific domain number.
Because the host (MAC) knows the order of packet transmission, only the timestamp is recorded (there is no need to record sequence number or other information). If required, the device has an option to record the 16-bit SequenceId, the 4-bit messageType field, and generate a 12-bit hash value for octets 20-29 of the PTP event message. The device can buffer four timestamps.
If enabled, an interrupt can be generated upon a Transmit Timestamp Ready.
One-Step Operation:
In some cases, the transmitter can be set to operate in a One-Step mode. For Sync Messages, a One-Step device can automatically insert timestamp information in the outgoing packet. This eliminates the need for host(MAC) to read the timestamp and send a follow up message.