Kinetis K64 IEEE1588 transmit timestamping

[ombra32]

Hi,

reference manual K64P144M120SF5RM at chapter "45.5.10.3 Receive timestamping" reports that for received frames the Ethernet MAC latches the timer value in correspondence of SFD field.

What happens for transmit frames? When is the timer latched?

This behavior is not explained at relative chapter "45.5.10.2 Transmit timestamping".

Regards,

Marco

[FelipeGarcia]

Hello Marco,

Unfortunately, this specific timing is not stated in documentation. However, as the Reference Manual indicates, the MAC records the timestamp for the frame in ENETn_ATSTMP. ENETn_EIR[TS_AVAIL] is set to indicate that a new timestamp is available.

Basically, what it means is that you will have to wait till ENETn_EIR[TS_AVAIL] is set to read the Timestamp of Last Transmitted Frame (ATSTMP).

For more information I also suggest you to check the following application note regarding IEEE1588 and Kinetis for reference.

https://www.nxp.com/docs/en/application-note/AN4332.pdf

Best regards,

Felipe

[ombra32]

Is there a way to know the exact position of timer latching for both transmit and receive packets, in relation to the Ethernet packet or related to TXEN/CRS_DV MAC signals?

[ombra32]

Can anybody help?

[FelipeGarcia]

Hello Marco,

Please accept my apologies for my late reply. I will try to ask this internally to see if we can get any feedback.

Sorry for the inconveniences.

Best regards,

Felipe

[ombra32]

Hi Felipe,

any news?

Regards,

Marco

[FelipeGarcia]

Hi Marco,

Sorry but this is the only information I could collect from internal.

When user writes the TS bit in Enhanced transmit buffer descriptor field, the Ethernet MAC will timestamp the frame that is ready to transmit and valid when EIR[TS_AVAIL] is set.

Regards,

Felipe

[FelipeGarcia]

Hi Marco,

I have escalated this question with our internal team. I will let you know whenever I received a response. Thanks for your patience.

Best regards,

Felipe

[ombra32]

I know how PTP works, and I looked up FRDM-K64F 1588 bare metal example provided in SDK 2.6.0.

PTP synchronization mechanism between 2 nodes works well.

But in my project I need to evaluate the accurate propagation delay between 2 nodes, connected via Ethernet cable in a point-to-point configuration.

To do so, I need to know the exact position of timer latching for both transmit and receive packets, in relation to the Ethernet packet or related to TXEN/CRS_DV MAC signals.

Regards,

Marco