WDT_A Operation
760
SLAU356I – March 2015 – Revised June 2019
Copyright © 2015–2019, Texas Instruments Incorporated
Watchdog Timer (WDT_A)
17.2.4 Watchdog Related Interrupts and Flags
The watchdog timer interrupt is handled through the enable, set, clear, pending flag of the Cortex-M4
NVIC channel that the WDT is mapped to. Refer to the appropriate device data sheet for the NVIC
channel number where the WDT is mapped. The functionality of the NVIC ensures that the related
interrupt pending flag is automatically cleared when the interrupt is serviced (unless another interrupt
occurs before the ISR is completed, which causes a re-entry into the same ISR).
When using the watchdog timer in the watchdog mode, a reset issued by the WDT may be mapped either
as the Hard Reset or the Soft Reset of the device. In addition, flags in the Reset Controller can be used to
determine if the WDT was indeed the cause of the reset. Refer to the appropriate device data sheet to
determine the reset channel of the Reset Controller that the WDT reset is mapped to. In addition, refer to
the
Reset Controller
chapter for details on how the flags of the various reset sources can be processed by
the application. These flags in the Reset Controller can be used by the reset service routine to determine
if the watchdog caused the device to reset. If the flag is set, the watchdog timer initiated the reset
condition, either by timing out or by a password violation. If the WDT flag is not set, the reset was caused
by a different source.
17.2.5 Clock Sources of the WDT_A
The WDT_A provides multiple options for the clock that can be used to source the counter, either in
watchdog or in interval timer mode (see
). The appropriate source can be selected by
controlling the WDTSSEL bits in the WDTCTL register.
(1)
Refer to the CS chapter for more details on the SMCLK, ACLK,
VLOCLK and BCLK settings as well as the possible clock sources for
the same.
(2)
Refer to
for details on clock source options during the
low-power modes of the device.
Table 17-1. WDT_A Clock Sources
WDTSSELx
Clock Source Selected (Watchdog and
Interval Timer Mode)
(1)
,
(2)
00
SMCLK
01
ACLK
10
VLOCLK
11
BCLK
17.2.5.1 Clock Fail-Safe Feature
If any of the sources for the clocks in
fails, the Clock System (CS) automatically switches over
to the appropriate failsafe option, so that the WDT operation can continue. Refer to the
Clock System (CS)
chapter for more details on the failsafe options for the various clock sources on the device.
17.2.6 WDT_A Operation in Different Device Power Modes
The devices have several active and low-power modes of operation. The requirements of the application
and the type of clocking that is used determine how the WDT_A should be configured.
17.2.6.1 WDT_A Operation in Active Modes
The WDT_A may be used either in watchdog or interval timer mode when the device is in one of the
active modes of operation. All clock sources as listed in
are available.
17.2.6.2 WDT_A Operation in LPM0 Modes
The WDT_A may be used either in watchdog or interval timer mode when the device is in one of the
LPM0 modes of operation. All clock sources as listed in
are available.