The highest speed of SPI?

Hello everyone

I have some DW1000 boards, and some boards have CLKPLL Loss-of-Lock event occasionally when I use the
SPI rate of 18MHz. When I use the SPI rate of 9 MHz or 14 MHz, this problem is not going to happen.
I follow the manual and wait until CLKPLL is locked to use the high speed SPI.

leo Theunissen said the SPI interface to the DW1000 uses the on-chip system clock. When the CLKPLL is locked this system
clock is provided by the CLKPLL and the maximum permitted SPI CLK is approx. 18 MHz;
And the manual said the SPI rate of up to 20 MHz can be used. So which one is the highest rate of SPI rate, 18MHz or 20MHz?

Thank you in advance

Too late, probably.
Anyway, I was using 20MHz on Atmel SAM4F.
On STM32 16MHz (L151) and 18MHz (F303, F429).


i use DWM1000 module with STM32L4 and i got full speed 20MHz. I also got CPLL lost during booting, but according to manual i write appropriate bit to clear it and then no problem.