LM3S6G11 Datasheet, PDF (492/827 Pages) Texas Instruments – Stellaris® LM3S6G11 Microcontroller

Watchdog Timers
OBSOLETE: TI has discontinued production of this device.
11.2.1
11.3
11.4
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 re-enabled, the 32-bit counter is preloaded with the load register value and not its
last state.
Register Access Timing
Because the Watchdog Timer 1 module has an independent clocking domain, its registers must be
written with a timing gap between accesses. Software must guarantee that this delay is inserted
between back-to-back writes to WDT1 registers or between a write followed by a read to the registers.
The timing for back-to-back reads from the WDT1 module has no restrictions. The WRC bit in the
Watchdog Control (WDTCTL) register for WDT1 indicates that the required timing gap has elapsed.
This bit is cleared on a write operation and set once the write completes, indicating to software that
another write or read may be started safely. Software should poll WDTCTL for WRC=1 prior to
accessing another register. Note that WDT0 does not have this restriction as it runs off the system
clock.
Initialization and Configuration
To use the WDT, its peripheral clock must be enabled by setting the WDT bit in the RCGC0n register,
see page 233.
The Watchdog Timer is configured using the following sequence:
1. Load the WDTLOAD register with the desired timer load value.
2. If WDT1, wait for the WRC bit in the WDTCTL register to be set.
3. If the Watchdog is configured to trigger system resets, set the RESEN bit in the WDTCTL register.
4. If WDT1, wait for the WRC bit in the WDTCTL register to be set.
5. Set the INTEN bit in the WDTCTL register to enable the Watchdog and lock the control register.
If software requires that all of the watchdog registers are locked, the Watchdog Timer module can
be fully locked by writing any value to the WDTLOCK register. To unlock the Watchdog Timer, write
a value of 0x1ACC.E551.
To service the watchdog, periodically reload the count value into the WDTLOAD register to restart
the count. The interrupt can be enabled using the INTEN bit in the WDTCTL register to allow the
processor to attempt corrective action if the watchdog is not serviced often enough. The RESEN bit
in the WDTCTL can be set so that the system resets if the failure is not recoverable using the ISR.
Register Map
Table 11-1 on page 493 lists the Watchdog registers. The offset listed is a hexadecimal increment
to the register’s address, relative to the Watchdog Timer base address:
■ WDT0: 0x4000.0000
■ WDT1: 0x4000.1000
Note that the Watchdog Timer module clock must be enabled before the registers can be programmed
(see page 233).
492
July 24, 2012
Texas Instruments-Production Data