Need a little help here.
I'm using K21FN1M0A on one of my custom design. My firmware consists of a bootloader and the actual firmware. I want to run my board in high gain crystal mode (I'm aware that a 1M Ohm resistor needs to be added). Here is the clock description of each piece of software:
Bootloader: use low power crystal mode
Firmware: Use high gain
1 - When I configured my firmware to work in low power crystal mode, everything started up fine. The bootloader started up and then the firmware.
2 - After I reconfigured my firmware for high gain crystal mode, the bootloader started (or at least I think it started). Then the firmware never ran (current draw dropped 8mA). I then used J-Link commander but it reported that JTAG Debug power domain was off
3 - After I reconfigured my firmware to high gain crystal mode, bootloader and firmware started ok.
So it is obvious that I have things working. My question is this
Why did going from low power to high gain crystal mode make the K21 hang? I couldn't really work it out from the clocking block diagram.
Much appreciated if somebody sheds some light on this. It has been bugging me for days.