GTS Ethernet Intel® FPGA Hard IP User Guide

ID 817676
Date 4/01/2024
Public

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4.8.2. TX 2-Step Timestamp Interface

The timestamp interface signals are valid when i_tx_valid and i_tx_startofpacket signals are high. To initiate a timestamp request, the i_ptp_ts_req signal must be high. You must also specify a fingerprint value in the i_ptp_fp signal.

The diagram below depicts the transmission of two packets. The first packet contains a two-step timestamp request with an assigned fingerprint, FP1.

Figure 45. IEEE 1588 TX 2-Step Timestamp Interface
  • The timestamp signals are only valid when i_tx_valid and i_tx_startofpacket are both high.
  • i_ptp_ts_req must be high to initiate a timestamp request.
  • The request must be accompanied by a fingerprint value on the i_ptp_fp port.
Note: The fingerprint values can be re-used when the timestamp for the packet is returned.
The diagram below depicts how a timestamp is returned for a packet when a 2-step timestamp request is issued:
Figure 46. 2-Step Timestamp: Receiving Timestamp for a Fingerprint
  • o_ptp_ets_valid is asserted to indicate that o_ptp_ets and o_ptp_ets_fp have a valid timestamp information.
  • o_ptp_ets is the timestamp, and o_ptp_ets_fp is the fingerprint (identifier) of the packet for which the timestamp is for.
Table 37.  2-Step TX Timestamp Interface SignalsThe timestamp is always in 1588 v2 format.
Signal Name Width Description
i_ptp_ts_req[0:0] 1

Request a 2-step timestamp for the current TX packet

1: Generate a TX timestamp for the current packet

TX MAC SOP-Aligned Client Interface:

i_ptp_ts_req[0] is valid only when i_tx_valid = 1 and i_tx_startofpacket = 1

i_ptp_fp[<w>-1:0]

<w> = Timestamp fingerprint width selected in GUI option

</w>

Fingerprint for current TX Packet

This bus is used to assign an 8 bit “fingerprint” to a TX packet that is being transmitted, so that the TX egress timestamp associated with the TX packet can be identified – the timestamp will be returned with the same fingerprint.

TX MAC SOP-Aligned Client Interface:

i_ptp_fp[<w>-1:0] is valid only when i_tx_valid = 1 and i_tx_startofpacket = 1

Used for both 2-step and 1-step PTP packets.

Intel recommends using a large range of fingerprints, to avoid the possibility of assigning the same fingerprint to 2 TX packets that are being processed.

o_ptp_ets_valid[0:0] 1

TX Egress Timestamp Valid

1: The fingerprint and egress timestamp ports are presenting valid output on this cycle.

o_ptp_ets[95:0] 96

TX Egress Timestamp

This bus is used to present an egress timestamp for the TX Packet that was transmitted with the fingerprint given by o_ptp_ets_fp

o_ptp_ets[95:0] is valid only when o_ptp_ets_valid[0] = 1

Used to present TX egress timestamps for both 2-step and 1-step PTP packets.

The timestamp is in 1588v2 format (96b).

The timestamp is for the packet whose fingerprint matches the fingerprint with the egress timestamp.

The timestamp indicates the estimated time at which the first bit of the start-of-packet block for the TX packet is transmitted from the tx_serial pin.

All timestamps are referenced to the copy of the Time-of-Day maintained on the EHIP.

o_ptp_ets_fp[<w>-1:0]

<w> = Timestamp fingerprint width selected in GUI option

<w>

TX Egress Timestamp Fingerprint

This bus presents the fingerprint for the current 2-step egress timestamp. The fingerprint can be used to determine which TX Packet the timestamp belongs with.

o_ptp_ets_fp[<w>-1:0] is valid only when o_ptp_ets_valid[0] = 1

Used to present TX egress timestamps fingerprints for both 2-step and 1-step PTP packets.