msp430f6726 XT1

xiang ji

Other Parts Discussed in Thread: MSP430F6726, MSP430F6723

Hello everybody!

I have a problem with starting XT1 crystal oscillator in 32.768 KHz mode on MSP430F6726. It just does not start. The scope attached to the ACLK monitoring pin shows No frequency .
I use none external caps on both XT1 pins.

I tried the code below on msp430f6726.

void main(void)
{

    WDTCTL = WDTPW | WDTHOLD;               // Stop WDT

__delay_cycles(0x600);
UCSCTL6 &= ~(XT1OFF);
UCSCTL6 &=~ (XTS);// enalbe XT1 and set XT1Drive
UCSCTL6 |= (XT1DRIVE_3); // enalbe XT1

while (SFRIFG1 & OFIFG) {   // check OFIFG fault flag
    UCSCTL7 &= ~XT1LFOFFG; // Clear OSC flaut Flags (DCOFFG+XT1LFOFFG+XT2OFFG)
    UCSCTL7 &= ~DCOFFG;
    SFRIFG1 &= ~OFIFG;        // Clear OFIFG fault flag
}                                          ; wait for crystal osc. to start

I would appreciate any advise for a direction to follow. The problem drives me crazy,

over 13 years ago

0 xiang ji over 13 years ago

Prodigy 70 points

0 Argail over 13 years ago in reply to xiang ji

Expert 2080 points

I think you simply forget to enable the ACLK ouput on pin, you have to set the correspondig PxSEL register.

0 xiang ji over 13 years ago in reply to Argail

Prodigy 70 points

thanks

I have enable the ACLK ouput on pin, The scope attached to the ACLK monitoring pin shows 10kHz frequency in VLO .

0 Argail over 13 years ago in reply to xiang ji

Expert 2080 points

Try to set the load capacitance to XCAP_3 (or to match load with crystal)

0 xiang ji over 13 years ago in reply to Argail

Prodigy 70 points

thanks!

I have trying to set the load capacitance from XCAP_0 to XCAP_3 .

I will try again.

0 xiang ji over 13 years ago in reply to xiang ji

Prodigy 70 points

I have try to set the load capacitance from XCAP_0 to XCAP_3 again. XT1 does not start.

0 Jens-Michael Gross over 13 years ago in reply to xiang ji

Guru 227245 points

xiang ji said:
I have try to set the load capacitance from XCAP_0 to XCAP_3 again. XT1 does not start.

Sometimes it's a hardware problem :)

Shortcuts between adjacent pins, flux remains under the MSP, bad soldering of the MSP pin - all this has happened in th epast and can cause the crystal to fail.

Layout of the PCB is also a factor. Short traces, no GND layer directly below these traces (because this adds stray capacitance)

0 Metin Gunsay over 13 years ago in reply to Jens-Michael Gross

Prodigy 10 points

I'm having this same problem. Under no circumstances can I get the XT1 to oscillate on the MSP430F6723. I've tried every combination of XCAP and XDRIVE. I've tried different crystals, including the one recommended in the data sheet. I've tried external caps. I've also tried building multiple boards. Nothing works.

I'm not new to the MSP family, and have never had these sorts of problems with XT1.

It also appears that the oscilator fault flags do not work.

I'm curious if anyone out there - including TI - has gotten the XT1 to work in LF mode?

I'd just like to know if it's possible or not, or if this is some sort of hardware bug.

0 xiang ji over 13 years ago in reply to Metin Gunsay

Prodigy 70 points

I has solved this problem. AUXVCC3 must be connected to Vcc. XT1 power is supplied by AUXVCC3. Wish this help you.

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