Hi Sathya! Have a look in the User's Guide , chapter 5. UCSCTL4 configures the sources for the internal clocks. In addition, UCSCTL5 gives you some dividers for the clocks. For using an external clock source, set XT2BYPASS in UCSCTL6. In bypass mode, P7.3 (XT2OUT) can be used as GPIO. P7.2 needs to have it's SEL bit set for using it as clock input. With having SEL cleared for P7.3 you now can use it as GPIO. This can be found in table 6-56 on page 92 in the datasheet . Dennis
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