SLAZ577V January 2014 – May 2021 MSP430F6749A
PMM Module
Functional
Device lock-up if RST pin pulled low during write to SVSMHCTL or SVSMLCTL
Device results in lock-up condition under one of the two scenarios below:
1) If RST pin is pulled low during write access to SVSMHCTL, with the RST/NMI pin is configured to reset function and is pulled low (reset event) the device will stop code execution and is continuously held in reset state. RST pin is no longer functional. The only way to come out of the lock-up situation is a power cycle.
OR
2) If RST pin is pulled low during write access to SVSMLCTL and only if the code that checks for SVSMLDLYIFG==1 is implemented without a timeout. The device will be stuck in the polling loop polling since SVSMLDLYIFG will never be cleared.
Follow the sequence below to prevent the lock-up for both use cases:
1) Disable RST pin reset function and switch to NMI before access SVSMHCTL or SVSMLCTL.
then
2) Activate NMI interrupt and handle reset events in this time by SW (optional if reset functionality required during access SVSMHCTL or SVSMLCTL)
then
3) Enable RST pin reset function after access to SVSMHCTL or SVSMLCTL
To prevent lock-up caused by use case #2 a timeout for the SVSMLDLYIFG flag check should be implemented to 300us.