back up during brown out

Hi Krish,

In your ISR, your case selection says "SVMLIFG".  But you should be looking for a value in SYSSNIV not the value of a flag.  SYSSNIV = 0x0002 represents SVMLIFG being set.  But your comment says "high side".  I think you want to look for SVMHIFG, which corresponds to a SYSSNIV value of 0x0004.  The SVMHIFG event almost certainly occurs before the SVMLIFG event during a power down.

You should also consider setting the high-side threshold higher, say for 2.4V Vin.  Use the highest setting for the voltage threshold.  That should give you as much notice as possible that power is going away.  I assume you have enough capacitance (or some other power control) to give you enough energy to write to flash as the supply voltage falls.

But still leave the low-side threshold low.  What MCU are you using?  Hopefully the low-side setting corresponds to 1.8V Vin.  (Not true on F54xx non-A models.)

For robustness I would still let the SVSL assert reset.  So use PMMRIE = SVMHIE + SVSLPE;

Jeff

Thanks Jeff for the reply. 

I increased the vcore output voltage using  PMMCTL0_L = PMMCOREV0+PMMCOREV1; and it started working.  Probably the vcore was not sufficient for the processor to

trigger SNMI interrupt.  I still need to figure it out. Here is the code.

void InitSNMIVector(void)

{

    // Open PMM registers for write access

    PMMCTL0_H = 0xA5;

    // Set SVS/SVM high side new level

    PMMCTL0_L = PMMCOREV0+PMMCOREV1;

    SVSMHCTL =   SVMHE + SVSMHRRL0+SVSMHRRL1+ SVSMHRRL2 ;

    PMMRIE =  SVMHIE;

    // Lock PMM registers for write access

    PMMCTL0_H = 0x00;

}

#pragma vector=SYSNMI_VECTOR

__interrupt void sysNmiISR(void)

{

   // a is just for testing

    uint8_t a[1];

    a[0] = 0xdd;

    FLASH_WriteFlash(a,(uint8_t *)FLASH_SEG_D_START,1);

    switch (SYSSNIV)

    {

        case 0x0002: 

            a[0] = 0xaa;

            FLASH_WriteFlash(a,(uint8_t *)FLASH_SEG_B_STOP,1);

            break;

        case 0x0004:       

            a[0] = 0x77;

            FLASH_WriteFlash(a,(uint8_t *)FLASH_SEG_C_STOP,1);

            break;

         default:

            break;

    }

}

Thanks....

Hi, I am using MSP430F2274 and I would like to implement a function that react "doing something" in case of supply problems (e.g. zapper).

I think that brown out could be used to detect such supply problems, but I did not find any datasheet, user guide or application note that describe BOR or SYSNMI_VECTOR or anything related to it.

Can you please help me?

Thanks!

Hi Marco

I was using MSP430f5418 for my application when i posted the above query.  

Please see slau144.pdf ( MSP430x2xx Family User's Guide (Rev. I) ). 

In Chapter 9, Supply Voltage Supervisor (SVS) it does mention that, 

The SVS can be configured to set a flag or generate a POR reset when the supply voltage or external voltage drops below a
user-selected threshold.  So, the bit you should be monitoring is SVSFG of SVSCTL register. 

However, it is  also mentioned that SVS is implemented in selected msp430x2xx devices.  

There is some problem downloading MSP430F2274 data sheet from TI website.  If you have this data sheet yourself  please check for SVS in it. 

Thanks,

Thank you for your reply Krish.

Now I am trying to do the same with a MSP430FR5969, entering in an interrupt if Vcc goes under a certain threshold.

I saw on slau367a.pdf that the register are different from MSP430x2xx. As far as I understand, the interrupt should be initialized in the SYSRSTIV interrupt vector register (or in SYSSNIV, I'm not sure) with interrupt event SVSHIFG. So I don't get how should I declare the interrupt, neither how should I set the thresholds level.

Is there someone who has experience with this?

Thank you.

Update:

I have just find out how to use SVS interrupt on MSP430FR5969. This is my code:

int main(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop WDT
  P1DIR=BIT0;                                                       // P1.0 Led
  PMMCTL0 = PMMPW + PMMLPRST + SVSHE;   // PMM password; SVSH triggers a system NMI; SVSH always enabled
  while(1)
  {
    __bis_SR_register(LPM3_bits + GIE);      //LPM3 with interrupt enabled
    P1OUT=0;                                     // Led off
  }
}

#pragma vector=SYSNMI_VECTOR;
__interrupt void SVS (void)
{
  switch (__even_in_range(SYSSNIV,0x12))       // Efficient switch-implementation
  {
    case  SYSSNIV_SVS:                                    // Vector 2: SVS
    P1OUT=BIT0;                                                 // Led on
    PMMIFG &= ~SVSHIFG;                                // Reset Interrupt Flag
    __bic_SR_register_on_exit(LPM3_bits);     // Exit LPM3
    break;
  }
}

This code does exactly what I expected: when the power supply drops below SVSH threshold it enters in the interrupt. I just discovered that the threshold is around 1.85V, and I was wondering if it is possible to change it (and how). Another issue is that when I try to rise the supply voltage after the interrupt the code turn off the led and enter again in LPM3, but it doesn't enter again in the interrupt if the power supply drops below SVSH threshold again. Do you know why?

Thank you!