SPRUJF2A March 2026 – March 2026 AM13E23019
The WWDT must be enabled before being configured for use through the PWREN register by writing the ENABLE bit with the correct KEY value to the PWREN register (see peripheral power enable).
The WWDT is configured through the WWDTCTL0 and WWDTCTL1 registers. These registers are password protected. Any register access (read or write) must be a 32-bit access. Write access must also include the corresponding password in the most significant byte (0xC9 for WWDTCTL0 and 0xBE for WWDTCTL1). Attempting a register write without the correct password or attempting a write with an access other than a 32-bit access generates a WWDT violation to SYSCTL, generating a BOOTRST. The password byte always reads as 0x00.
The WWDT is disabled and cleared after a SYSRST, which resets the peripherals and CPU state but does not trigger execution of the BCR, or a BOOTRST. A WWDT violation does not generate a SYSRST. Please see Resets and Device Initialization for more information on resets.
The WWDTCTL0 register sets the static configuration of the WWDT, including: the clock divider (CLKDIV), the timer period (PER), the two closed window percentages (WINDOW0 and WINDOW1), the timer mode (MODE), and the stop-in-sleep status (STISM). The WWDTCTL1 register controls which closed window percentage is being used by the WWDT through the WINSEL bit.
The first write (with a key match) to the WWDTCTL0 register enables the WWDT. Once the WWDT is enabled, the WWDTCTL0 register becomes write protected. Any attempt to write to the WWDTCTL0 register after the WWDT is enabled generates a WWDT violation to SYSCTL. In order to reconfigure the WWDT after it is enabled, the device must undergo either SYSRST or BOOTRST. The RUN bit in the WWDTSTAT register indicates that the WWDT is running.
WWDT Diagram shows the WWDT functional block diagram.