LM3S9B81 Datasheet, PDF (472/1155 Pages) Texas Instruments – Stellaris® LM3S9B81 Microcontroller

Watchdog Timers
12.1
Block Diagram
Figure 12-1. WDT Module Block Diagram
Interrupt
System Clock/
PIOSC
Control / Clock /
Interrupt
Generation
WDTCTL
WDTICR
WDTRIS
WDTMIS
WDTLOCK
WDTTEST
WDTLOAD
32-Bit Down
Counter
0x0000.0000
Comparator
WDTVALUE
Identification Registers
WDTPCellID0
WDTPCellID1
WDTPCellID2
WDTPCellID3
WDTPeriphID0 WDTPeriphID4
WDTPeriphID1 WDTPeriphID5
WDTPeriphID2 WDTPeriphID6
WDTPeriphID3 WDTPeriphID7
12.2
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.
After the first time-out event, the 32-bit counter is re-loaded with the value of the Watchdog Timer
Load (WDTLOAD) register, and the timer resumes counting down from that value. Once 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.
472
June 29, 2010
Texas Instruments-Advance Information