Hi Xia bin
Not, unfortunately, SPLL reference frequency range is Min 8MHz and max 16MHz, so, you can't use it with an osc of 4M. Sorry for the inconveniences:
https://www.nxp.com/docs/en/data-sheet/S32K1XX.pdf#page=33
Best regards
Jorge Alcala
Hi Xia bin
Not, unfortunately, SPLL reference frequency range is Min 8MHz and max 16MHz, so, you can't use it with an osc of 4M. Sorry for the inconveniences:
https://www.nxp.com/docs/en/data-sheet/S32K1XX.pdf#page=33
Best regards
Jorge Alcala