Hello,
Currently I'm working on a project that requires a synchronized clock signal between multiple devices connected through Ethernet.
The logic solution for this is PTP, and using linuxptp I was able to archive synchronous PPS on PG8 pin between devices with a jitter smaller than 1us for 1Hz.
Now the problem is that the requirement for PPS frequency is not 1Hz but a OR between a 100Hz and 1.25Hz (see attached image). From documentation, flexible PPS output may be the solution and started testing it by generating the 100Hz signal. Here is were I found the issue, after program PPSCMD[3:0] with start I notice that the 100Hz signal starts to drift slowly (around 20us/s).
Now strange part is if I use fixed PPS (bit PPSEN0 of MACPPSCR cleared) with any frequency (1Hz to 16kHz with digital rollover) there is no drift. From my understanding the reference clock for pps is the same as system time thus adjusted by ptp protocol for maintaining synchronization.
Is my assumption correct or when flex pps is enabled a different reference clock is selected?
Best regards
