SLAU962A December 2025 – June 2026 MSPM33C321A , MSPM33C321A-Q1
After a cold start, the NRST pin is configured in NRST mode. The NRST pin must be high for the device to boot successfully. There is no internal pullup resistor on NRST. External circuitry (either a pullup resistor to VDD or a reset control circuit) must actively pull NRST high for the device to start. After the device is started, a low pulse on NRST <1 second in duration triggers a BOOTRST. If a low pulse on NRST is held for >1 second, a POR is triggered.
Some low pin count devices support reconfiguring the NRST pin to be a GPIO pin. See the pin configuration of the device-specific data sheet to see if GPIO functionality is shared with NRST. Application software can disable the NRST functionality of the NRST pin, allowing GPIO functionality to be enabled. To disable NRST, set the DISABLE bit in the EXRSTPIN register along with the KEY. Then configure IOMUX for the desired functionality.
After the NRST pin function is disabled, only after a POR reset can the NRST pin function be re-enabled.