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MSP430F1232: Wait before setting DCO

Sh.Sasaki
Guru 13625 points
Part Number: MSP430F1232

Hi,

If the customer's board is set to DCO immediately after the power is turned on, the device will not operate properly. (CPU stopped)

After turning on the power of this board, insert a Wait of about 100ms, and then set the DCO, the device will operate correctly.

XT1 is a 32kHz crystal.

Do you know why their boards work correctly when they insert wait?

Is it because it takes time for the crystal to oscillate stably?

Best regards,
Sasaki

  • 0
    Guru 20475 points

    The DCO is the default source for MCLK after reset so there must be some error in the details of what is being done to the clock. But you haven't shown those details. Be sure to check device errata.

  • +1
    Guru 91390 points

    If your power ramp is slow, and you speed up the DCO too early, you might end up running too fast for the (momentary) Vcc. [Ref data sheet (SLAS361D) p. 16 ("recommended operating conditions")] This could result in erratic behavior and maybe a CPU freeze.

    A 32kHz crystal can take 100+ms to start up, but this seems (in itself) unlikely to cause a CPU freeze.

  • 0 in reply to Bruce McKenney47378
    Guru 13625 points

    Thank you for your advice.

    They are running Set_DCO(fet120_fll_01.c) immediately after powering on.

    I ask them to check around the power supply again.

    Best regards,
    Sasaki

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