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MSP430F5659: why LOCKBAK bit cleared in BAKCTL register during XT1 selection

Muthiah K
Prodigy 50 points

Part Number: MSP430F5659

Hi,

I referred a example code for MSP430F5659 for selecting XT1 as clock source. I saw that the LOCKBAK bit was cleared in the BAKCTL register before touching the UCSCTL registers. (Attached reference)

Could you please explain the significance of clearing the LOCKBAK bit in the BAKCTL reg while choosing the XT1 input?

MSP430F665x Demo - XT1 sources ACLK:

  • 0
    TI__Mastermind 28195 points

    Hi Muthiah,

    This check and clearing of the LOCKBAK bit verifies that the battery backup system registers (and by extension the LF Crystal settings in the UCS register) may be modified.

    Per section 3.2 of the user's guide, restricting access to the battery backup control system, which occurs automatically when powered by VBAT, also prevents modifying LF Crystal settings.

    Best Regards,
    Brandon Fisher

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