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MSP430G2152 watchdog source in LPM4

AlanZhang
Intellectual 515 points

Other Parts Discussed in Thread: MSP430G2152

Hi, 

I am using the watchdog in MSP430G2152 chip. 

After reading the MSP430x2xx user guide, I am confused with the default clock source of the watchdog.  

According to datasheet, when bootup after reset, LFXT1Sx is 00, the watchdog should use SMCLK as clock source. When it enter LPM4 mode, the SMCLK is stopped. In real-time testing, the watchdog still expires and reset the chip.

Question: what is the default clock source for watchdog at boot-up/reset for MSP430G2152?  

Alan

  • 0
    Guru 227245 points

    AlanZhang said:
    what is the default clock source for watchdog at boot-up/reset for MSP430G2152?  

    It is DCO->SMCLK->WDT

    You cannot stop a clock chain that is in use. Your LPM request is partly ignored as long as the watchdog is active, requests SMCLK and SMCLK is driven by DCO. DCO remains active, SMCLK remains active. Watchdog is still working.

    See fig. 10-1 in the users guide WDT chapter (Clock request logic). Since WDTTMSEL is an input to the request logic too, i think that this unconditional clock request is only issued if the watchdog runs in watchdog mode (and is not stopeed)

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