Once a provided demo app. suddenly ceased to work. I debugged it and it seems that the internal CGM PLL that provides clock for the FR module doesn't lock.
I wrote a small program that tested all the possible combination of SYNR and REFDIV values, but the PLL never locks.
The rest of the chip seems to work.
??? What happened ???
As a workaround I will try to put a 80 MHz quartz oscillator instead of the 4 MHz crystal on the board. That should clock the FR module according to the manual. But, will it work as a clock to the rest of the MCU? I can of course use the (other) PLL to even divide the clock frequency as well, but I mean, 80 MHz isn't to much for the EXTAL input?
Another question on side is a that some components are mounted on the EVB around a pin called XFC. This pin of the MCU is not even named in the ref. manual. It is marked as NC (not connected) What is it and what are those components for?