For a low-cost device in M0 like MSPM0C110x, there are no hardware registers available to help implement SWD protection with a password, but only the fully open or completely disabled options can be chosen. However, with the popularity of cybersecurity, more and more applications, especially for the automotive market, are requesting this password-protected function. This application note proposes a new way to realize this security function based on software for a low-cost device, which does not have hardware to support the device.