MSP430FR2433: MSP430FR2433 / external clock input / bypass mode

Dirk Ruth said:

I want to use an external crystal oscillator with 16 MHz on the XT1IN pin (XT1BYPASS mode).
Is this possible? I can't really figure it out from the data sheet.

The MSP430FR4xx and MSP430FR2xx Family User's Guide (Rev. I) contains the following note for the XTS bit in the Clock System Control Register 6:

Using a MSP-EXP430FR2433 I started a debug session, and tried to use the CCS Register view to set the XTS bit in the CSCTL6 register. Attempting to set the XTS bit failed, and always read back as zero.

Was able to set the XTS1BYPASS bit which shows debugger writes to the CSCTL6 register were working.

Giving that unable to set the XTS bit this means the MSP430FR2433 doesn't support XT1 HF mode, and therefore don't think a an external 16 MHz input on the XT1IN pin will work. Also, the MSP430FR2433 has no mention of XT1 HF mode.

Thank you for your help.
Is the XT1 HF mode only necessary for an HF crystal or also for an external HF oscillator?

Dirk Ruth said:

Is the XT1 HF mode only necessary for an HF crystal or also for an external HF oscillator?

Looking at the datasheet for MSP430FR2355 there are separate parameters ^fXT1,SW "XT1 oscillator logic-level square-wave input frequency":

And ^fHFXT,SW "HFXT oscillator logic-level square-wave input frequency, bypass mode":

Whereas the MSP430FR2433 datasheet has only ^fXT1,SW specified, which I take to mean the MSP430FR2433 doesn't support a 16 MHz  oscillator logic-level square-wave input on the XT1IN pin. Hopefully a TI employee will respond if I am wrong.

I see that the XT1 HF mode is much better specified with min/max values than the LF mode with typical values.

As an alternative, do you think it would work to use the external clock (UCLK) for the eUSCI in UART mode (UCA1CLK/UCA1TXD/UCA1RXD).

The aim is to provide a stable UART connection over the entire temperature range ASAP after start-up.