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MSP430F5528 XT1 setup

Todd Anderson78572
Guru 14640 points

Reference: http://e2e.ti.com/support/microcontrollers/msp430/f/166/t/19726.aspx

 If I read these posts correctly, I think that there is added delay between the "Port select XT1" and "Switch XT1 On" to allow the oscillator to stabilize before using, correct?

On the F5529, the XT1 is defaulted to "on" on powerup. Does that mean it should be turned off, then allowed to stablize, then turned on?

I also need to set up XCAP to be different that default. So, should I

1. Turn off XT1.

2. Port select Xt1.

3. Wait for stabilization.

4. Turn on XT1.

5. Then route to RTC, ACLK and any other place it is being used

  • 0
    Guru 227245 points

    No, there is no delay needed between selecting the XT1 function and clearing the XT1OFF bit. However, after both is done, the crystal will take some time to stabilize. Until it has done a certain number of oscillations without timeout (1024 for HF and 8192 for LF operation), you won’t be able to clear the XT1OFFG or LFXT1OFFG bit (and therefore the OFIFG bit). Which will prevent XT1 from being used as source for anything (instead, DCO is used or, in LF mode, REFO, to source FLL, ACLK etc.) and setting the oscillator source select bits in the clock module has no effect (but takes effect once you successfully cleared OFIFG)

    See the ‘fail-safe operation’ chapter in the users guide.

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