AnsweredAssumed Answered

How to generate usable system clock in PTP/1588 slave

Question asked by Eza Gall on Apr 1, 2020
Latest reply on Apr 14, 2020 by Sabina Bruce

Hi, on the iMx RT there is an example mentioned in AN12149 that synchronizes a 1PPS timer to a network clock. 

In theory I can use the 1PPS output to generate a usable network synchronized system clock (such as 6.144Mhz or 24Mhz) by using an external PLL that accepts 1PPS input however all the IC's available to achieve that are super expensive so are not an option. I'm also concerned that using the 1PPS to generate a stable local system clock will have too slow response and not adjust for short duration drift in the network clock.

 

There must be a way to generate a system clock either without an external PLL or with a lower cost external clocking chip.

 

1. Is it possible to change the "Adjustable Timer Module" in the 1588 block to a much higher frequency than 1PPS without too much penalty in resultant sync accuracy? This higher freq clock could be fed back into the iMx (say into CLK1 pin) then have internal iMx PLL (PLL3 or PLL5) generate internal clock? 

 

2. Is it possible to change the "Adjustable Timer Module" in the 1588 block to a much higher frequency than 1PPS and feed it directly to an output pin (rather than through an interrupt)?

 

Any thoughts welcome.

Outcomes