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RTC fuctionality(Data retention and ticking) in Reset state of MSP430F5325

sunil hs
Intellectual 525 points
Other Parts Discussed in Thread: MSP430F5325

Hi,


I am using MSP430F5325 for my project. I have few queries.

1. Does internal RTC runs on DVCC or AVCC.

2. Apart from manual reset on reset pin/watchdog reset,Is there a Software reset command to reset the controller.

3. While RTC is running ,on provide software Reset  command will the RTC current value ill be retained and continue to tic or lost.

4.If my controller is in LPM03 and the voltage drops below 2.2V(Below Wake up voltage) will the RTC module run?

Looking forward for reply


Best regards,

Sunil H S

  • 0
    TI__Mastermind 18320 points
    Sunil,

    TI-RTOS does not have any direct support for the MSP430 RTC, so I have moved this thread over to the MSP forum in hopes that you will get a faster response there.
  • 0
    Expert 1595 points

    Hi,

    1. The RTC will operate from the DVCC voltage

    2. The family user guide for the MSP430F5xx and MSP430F6xx has section 1.2 System Initialisation and reset, that mentions it is possible to activate a software POR. You will need to do a bit more research to determine exactly how to do this. Alternatively it should be possible to directly jump to the RESET vector code to do a "sofware only" reset that does not change the hardware registers. 

    3. Generally the RTC will be stopped with any form of Reset BOR, POR or PUC. If you try to use a jump to the reset vector, you may be able to keep the RTC running, but you will need some careful handling of the initialisation code.

    4. If it is set up correctly both the uP and the RTC should operate down to 1.8V 

  • 0 in reply to Roy Deabill
    Intellectual 525 points
    Thank you Roy,

    1) Vcore also runs on DVCC. Correct?
    2) I have a situation where in my DVCC pin has constant 3.3V and AVCC drops from 3.3V to 0V (for 10Min). Now my doubt is "Since the AVCC is at different voltage and DVCC is at different voltage, will the controller turns off or any other hardware registers loose the data(as in PUC reset state)".As whole i would like to know the significance of AVCC and effects when there is a diffrenece in voltage between DVCC and AVCC.
    3)Can u also tell are there any modules operating on AVCC . Dose ADC operate only on AVCC?
    Looking forward for reply


    Best regards,

    Sunil H S
  • 0 in reply to sunil hs
    Expert 1595 points
    Hi,

    Vcore is generally powered from the DVCC pin, but has an internal regulator so that the Core can run at a reduced voltage if that is required by the application. Often using a lower Vcore will reduce the maximum frequency that the processor can run at. This is explained in section 2.2.4 of the family user guide.

    Generally the AVCC pin is connected to the DVCC pin, and this condition is used for all of the parameters defined in the datasheet. The two pins are separated to allow for different decoupling capacitors to be fitted close to each of the pins so that noise introduced by the digital circuits on DVCC can be filtered out and not appear at the AVCC pin and cause noise on the ADC readings.

    I do not recall ever seeing any data that provides an indication of what happens if you set AVCC to 0V. What is your reason for not simply connecting both pins together with the required decoupling capacitors on each pin?

    The ADC and REF modules are definitely powered from the AVCC pin. This is inferred in the main datasheet where the parameters of both of these modules are specified, with reference to AVcc rather than DVcc which is used for the other modules.

    Overall I would recommend that you leave both pins at the same voltage. To ensure minimal current consumption your software should ensure that ADC and REF are disabled unless they are in use, so the current drawn by AVCC will be minimal.
  • 0 in reply to Roy Deabill
    Intellectual 525 points
    Thanks a lot Roy.It gave me good understanding on the same.

    Best regards,
    Sunil H S
  • 0 in reply to Roy Deabill
    Guru 227245 points
    "I do not recall ever seeing any data that provides an indication of what happens if you set AVCC to 0V."
    AVCC and DVCC are internally connected by clamp diodes. So if one of them is unpowered, it is indirectly powered by the other through diodes. Until you blow the diodes due to overcurrent. Which will likely happen if you tie AVCC to 0V and DVCC to 3.3V.
    The maximum difference between the two is the diode voltage at maximum rated current. Assuming 0.2V is safe. This allows for decoupling GND and supply ripple (separate AGND routing and DVCC->AVCC low-pass filtering), but you cannot switch off the supply and even shouldn't run the two from different supply sources (due to different ramp-up times).

    A software reset (different kinds) can be triggered in the power management module. B aware of the password protection - else an attempt to trigger a BOR will only result in a PUC due to password violation. :)

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