From the MSP430FR4133 datasheet:
...but when I set this bit and disable an external XTAL then I see power usage go up by ~20uA, which suggests that the chip is, in fact, failing over to the REFO clock.
Is the XT1FAULTOFF bit actually present in MSP430FR4133 device as show in the datasheet?
If not, can you suggest a way to avoid having REFO clock running when in LPM3 in a system with no external XTAL available?
Since there is no way to set ACLOCK to VLO on this part, I was hoping to set ACLOCK to XTAL and then set XTALBYPASS on so there was effectively no XTAL clock running to save the 20uA of the REFO clock running to drive ACLOCK which is unused (No peripherals are using ACLOCK). But I needed to XT1FAULTOFF to prevent falover to REFO that would then waste 20uA.