The program sequence monitor (PSM) provides an additional check to determine if the system software has executed in the expected manner without error. The PSM includes two task signature registers (0 and 1). The PSM is an option for the basic window mode only.
The program sequence begins when the software initializes the Task_Sig0 register. If the task signature 0 register write completes successfully, then the software writes the same value to the Task_Sig1 register during the second (open) window. When the watchdog timer restarts, it compares the two task signature registers. If the two registers do not match, then it is considered a bad event that might lead to the system reset and SWDTn_RST assertion.