The 03/08/2022 19:10, Andrew Lunn wrote: > > > > So this is a function of the track length between the MAC and the PHY? > > > > Nope. > > This latency represents the time it takes for the frame to travel from RJ45 > > module to the timestamping unit inside the PHY. To be more precisely, > > the timestamping unit will do the timestamp when it detects the end of > > the start of the frame. So it represents the time from when the frame > > reaches the RJ45 to when the end of start of the frame reaches the > > timestamping unit inside the PHY. > > I must be missing something here. How do you measure the latency > difference for a 1 meter cable vs a 100m cable? In the same way because the end result will be the same. Lets presume that the cable introduce a 5ns latency per meter. So, if we use a 1m cable and the mean path delay is 11, then the latency is 11 - 5. If we use a 100m cable then the mean path delay will be 506(if is not 506 then is something wrong) then the latency is 506 - 500. > Does 100m cable plus 1cm of track from the RJ45 to the PHY make a difference > compared to 100m cable plus 1.5cm of track? In that case I don't think you will see any difference. > Isn't this error all just in the noise? I am not sure I follow this question. > > Andrew -- /Horatiu
