How to use the ptp modules?

[IncognitoChap]

Hi Alex,

I would like to implement a PTP slave clock in my FPGA but I am not quite sure on how to use the few ptp blocks that you have written. Is there a prerequisite that I need to know before using the few ptp blocks? If you have a reference design - that hook up the few modules together - to share, it will be very much appreciated.

I will be glad if you can elaborate on this matter.

Thanks!

[alexforencich]

The blocks here are only for the PTP clocking and timestamping infrastructure. I do not have a full implementation of PTP including parsing PTP protocol packets, time servo, grand master selection, etc, etc. The blocks here were developed to enable PTP support in Corundum, which uses linuxptp for the rest of the stack. If you need a self-contained solution, then you'll probably want to use a soft core of some sort due to the complexity of the higher layers of the protocol.

[IncognitoChap]

Hi Alex,

Thanks for the swift response. I have an additional question. In ptp_clock.v, I see that you are expecting a 96/64 bit timestamp input. I think it means that another module/hardware is performing the timestamp gathering and this block is to just do the adjustment? In other words, this is a clock adjustment module. Is my understanding correct?

Thank you.

[alexforencich]

ptp_clock generates the clock, and you can load a new value and adjust the period in order to synchronize it. It's basically a fancy counter that you can load and adjust the step size. The timestamping would be done by the Ethernet MAC modules - they accept the current PTP time from the PTP clock, and then return the packet time stamps. You can use the ptp_cdc module to transfer the output of ptp_clock across clock domains, for example to transfer the PTP time from a logic clock domain into the MAC TX and RX clock domains.

[IncognitoChap]

Ah... okay. I think I got the gist of it. Thanks Alex!