Control / Clock /
Interrupt Generation
WDTLOAD
WDTVALUE
Comparator
32-Bit Down Counter
0x0000.0000
Interrupt/NMI
System Clock/
PIOSC
Identification Registers
WDTPCellID0
WDTPCellID1
WDTPCellID2
WDTPCellID3
WDTPeriphID0
WDTPeriphID1
WDTPeriphID2
WDTPeriphID3
WDTPeriphID4
WDTPeriphID5
WDTPeriphID6
WDTPeriphID7
WDTCTL
WDTICR
WDTRIS
WDTMIS
WDTLOCK
WDTTEST
Functional Description
1799
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Watchdog Timers
Figure 28-1. WDT Module Block Diagram
28.3 Functional Description
The Watchdog Timer module generates the first time-out signal when the 32-bit counter reaches the zero
state after being enabled; enabling the counter also enables the watchdog timer interrupt. The watchdog
interrupt can be programmed to be a nonmaskable interrupt (NMI) using the INTTYPE bit in the WDTCTL
register. After the first time-out event, the 32-bit counter is reloaded with the value of the Watchdog Timer
Load (WDTLOAD) register, and the timer resumes counting down from that value. When the Watchdog
Timer has been configured, the Watchdog Timer Lock (WDTLOCK) register is written, which prevents the
timer configuration from being inadvertently altered by software.
If the timer counts down to its zero state again before the first time-out interrupt is cleared, and the reset
signal has been enabled by setting the RESEN bit in the WDTCTL register, the Watchdog timer asserts its
reset signal to the system. If the interrupt is cleared before the 32-bit counter reaches its second time-out,
the 32-bit counter is loaded with the value in the WDTLOAD register, and counting resumes from that
value.
•
If WDTLOAD is written with a new value while the Watchdog Timer counter is counting, then the
counter is loaded with the new value and continues counting.
•
Writing to WDTLOAD does not clear an active interrupt. An interrupt must be specifically cleared by
writing to the Watchdog Interrupt Clear (WDTICR) register.
•
The Watchdog module interrupt and reset generation can be enabled or disabled as required. When
the interrupt is reenabled, the 32-bit counter is preloaded with the load register value and not its last
state.
•
The watchdog timer is disabled by default out of reset. To achieve maximum watchdog protection of
the device, the watchdog timer can be enabled at the start of the reset vector.