Hi MartinL,
I came across this thread a short while ago:
https://forum.arduino.cc/index.php?topic=553612.0
In that thread, you discuss using the ALARM0 compare to generate a 1 Hz interrupt (post #2). Later (post #6 and #8) you describe avoiding the 6ms delay caused by the SYNCBUSY wait. My question relates to sleeping immediately after incrementing the ALARM0 compare register before the SYNCBUSY is complete. Will the sleep be delayed until the SYNCBUSY is complete in that instance or does the device go to sleep right away?