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MSP430F5507: No communication start of UART at low temp(0℃)

Part Number: MSP430F5507

My customer is facing the issue of "no communication start of UART at low temp(0℃)" on their system.

The UART communication using the USCI port did not start when the power was turned on occurred,

UART is working correctly at room temperature (23 ° C) or high temperature (45 ° C), but it occurs at low temperature.

I have attached the photo of  the waveform observed by the oscilloscope at power-on,
Yellow: A signal that outputs Hi / Lo inversion every 200ms while operating with PU.1.
Blue and green: UCA1TXD, after this it should respond after boot, but the signal is falling to Lo (Hi-Z)
Red: UCA1RXD receives startup notification from the system's Main CPU after this

The customer expect the output of TXD drops to Lo 2s after the power is turned on, which is a clue to the problem phenomenon.

Could you advise what we should check like register setting and clock tree selection ?  

since we request customer to do it .

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