MSP430 Watchdog Reset does not reset all registers (PUC & POR)

Hi Tom,

PUC or power-up clear is triggered by either a POR or WDT timer expiration in watch dog mode or WDT/flash/PMM password violations or an invalid fetch from a peripheral area. The default values after a PUC are indicated by -0 or -1 in the respective register definitions in the users guide.

One of the ways to determine if a PUC occured is to use the SYSRSTIV (reset interrupt vector) present on the F5xx/F6xx devices which can be used to determine the cause of the last reset that happened - BOR/POR/PUC.

Regards,

Bhargavi

Jens-Michael,

Good answer, it looks like the MSP430 designers have tried to separate hardware errors (which require a full hardware reset) from software "faults" (which do not need a reset). However this does not look optimal to me, as suppose you get a runaway program which can potentially do anything before it gets stuck and triggers the watchdog. To recover from the error you really have to review the datasheet register listing very carefully and make sure that you set all the registers bits to the correct state.

Tom Harris said:

However this does not look optimal to me, as suppose you get a runaway program which can potentially do anything before it gets stuck and triggers the watchdog. To recover from the error you really have to review the datasheet register listing very carefully and make sure that you set all the registers bits to the correct state.

It's like with the watchdog. If you don't disable it at the beginning of your program, you might encounter unexplainable resets. Unexplainable until you discover teh WDT and handle it properly.

However, the MSPGCC was disabling the WDT on default during startup (to avoid a WDT reset while initializing the variables on devices with much ram). This was worse, because there was no way for plain C users to have the WDT on all the time (for ESD based crashes in harsh environment,). I had to write my own version of the startup code in assembly, which isn't for everybody. If it were disabled as default in hardware, there would have been nothing I could have done at all.

And I agree, yes, a good program should init all parts of the MSP (including those not really used or not specifically used) which may not be in default ocndition after a software (but not hardware) reset. On newer MSPs, there is even a way to force the different reset types. So you can simply check what the cause of the last restart was, and then force a BOR, resetting everything.

Hi Bhargavi,

                      These is use full to me. I have Some doubt in MSP430FG437 BASED PULSE OXIMETER PROGRAM. Please clear it.

1) In SaO2 Look table

            // SaO2 Look - up Table

            const unsigned int Lookup [43] = { 100, 100, 100, 100, 99, 99, 99, 99, 99, 99, 98, 98 98 98, 98, 97, 97, 97
                                                                           97, 97, 97, 96, 96, 96, 96, 96, 96, 95, 95, 95, 95, 95, 95, 94, 94, 94,
                                                                            94,94, 93, 93, 93, 93, 93};

           What value of input will we get 100 as output in the lookup table? So also for 93 - 99 in the lookup table. what is the panic alarm that we may get if output of the Pulsoximeter source abnormal value?

2) In FIR filter

//FIR filter coefficient for removing 50/60Hz and 100/120Hz from the signals
#if 0
static const int16_t coeffs[9] =
{
    5225,
    5175,
    7255,
    9453,
    11595,
    13507,
    15016,
    15983,
    16315
};
#else
static const int16_t coeffs[12] =
{
    688,
    1283,
    2316,
    3709,
    5439,
    7431,
    9561,
    11666,
    13563,
    15074,
    16047,
    16384
};
#endif

What is referred to by the value 0 and these filter coefficient details?

         Regards

       Arun Prasad, M.D.,

   Silicon Technologies.

Hi Arun,

#1

The SaO2 is computed as the log ratios of the infrared and visible red ac signals measured in the pulsox set-up. And this log ratio is subtracted by the offset in order to correlate to the lookup table values.

As mentioned in slaa458 - SaO2 look-up table defines the relationship between the ratio R and %SaO2 values and was first generated by extrapolating values from the “Empirical and Theoretical Ratio (R) to SaO2” curve, and then verified by taking two sets of readings of few subjects – first the correct SaO2 values from an actual pulsoximeter equipment (a Masimo instrument) and then the Ratio values (R) from the pulsox board.

The companies who sell pulsoximeters as their end products develop their own SaO2 look-up table and the SaO2 look-up table used in the app note is a very simple implementation and is used for demo purposes only.

#2

Shall have to take a look at this and get back to you.

Regards,

Bhargavi

Hello Bhargavi, have you answered the #2 question somewhere else??,  i've been having difficulties trying to understand the whole thing about the  FIR filter coefficients. I read that  #if 0 ;  is used to disable certain parts of code in a programme so the coefficients to be used would be those after #else  ,but when I checked the frequency response, it doesn't look like a LPF of 6 Hz passband with an attenuated band of 50 Hz and above .

Thanks in advance