Watchdog Timer
UG0331 User Guide Revision 15.0
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20.2.3.2.2 Cortex-M3 Processor in Sleep Mode
The Cortex-M3 processor can be put into a low-power state by entering sleep mode. The processor exits
sleep mode when an interrupt occurs. The watchdog timer can be configured to generate an interrupt if
its counter value moves from the permitted to the forbidden window (at the WDOGMVRP level) when the
Cortex-M3 processor is in sleep mode. The processor wakes up and refreshes the watchdog timer and
then goes back into sleep mode. The WDOGWAKEUPINT output from the watchdog timer is used for
this interrupt. The WAKEUPINTEN control bit in the
is used to enable/disable
generation of the WDOGWAKEUPINT interrupt, with the default setting being disabled.
20.2.3.2.3 Programming FPGA Fabric/eNVM
The watchdog timer has an input port called PROGRAMMING, which is connected to the
watchdog_freeze signal in the microcontroller subsystem (MSS). The watchdog_freeze is asserted by
the system controller under certain conditions, such as when programming the eNVM. When the
PROGRAMMING port is asserted, the watchdog timer counting is paused. When the PROGRAMMING is
de-asserted, the watchdog timer behaves as if it has just come out of reset.
20.2.3.2.4 Flash*Freeze
During Flash*Freeze, the watchdog timer continues to operate unless the Cortex-M3 processor enters
Sleep mode. In Sleep mode, the watchdog timer stops counting and holds the current value.
20.2.3.3 Watchdog Timer Interrupts
There are two interrupt outputs in the watchdog timer: WDOGTIMEOUTINT and WDOGWAKUPINT.
20.2.3.3.1
WDOGTIMEOUTINT
This interrupt is asserted when a counter timeout occurs and an interrupt instead of reset generation is
selected. This interrupt is connected to the non-maskable interrupt (NMI) input of the Cortex-M3
processor and can also be exposed to the FPGA fabric.
20.2.3.3.2
WDOGWAKEUPINT
This is asserted (if enabled) on crossing the WDOGMVRP level when the SLEEPING input is asserted.
This interrupt is mapped to the interrupt request 0 (INTISR [0]) in the Cortex-M3 processor interrupt
controller.
20.3
How to Use the Watchdog Timer
This section describes how to use the watchdog timer in an application.