SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
Some of the RTI features described in this section may not be supported on this family of devices. For more information, see RTI Not Supported Features.
Digital windowed watchdog (DWWD) timer is implemented using the digital windowed watchdog function of the RTI modules. Real time interrupt functionality is not supported. In this mode, the timer should default to disabled and user can adjust the period as desired before enabling the watchdog.
In addition to the time-out boundary configurable via the digital watchdog (DWD), some applications may also want to configure the start-time boundary of the watchdog. This is enabled by the digital windowed watchdog (DWWD) feature.
Functional Behavior
The DWWD opens a configurable time window in which the watchdog must be serviced. Any attempt to service the watchdog outside this time window, or a failure to service the watchdog in this time window, will cause the watchdog to generate either a reset or a non-maskable interrupt to the CPU. This is controlled by configuring the RTI_WWDRXNCTRL register. As stated earlier, when the watchdog needs to be enabled by software, the watchdog counter is disabled on a system reset. When the DWWD is configured to generate a non-maskable interrupt on a window violation, the watchdog counter continues to count down. The RTI_INTR_WWD interrupt handler needs to clear the watchdog violation status flag(s) and then service the watchdog by writing the correct sequence in the watchdog key RTI_WDKEY register. This service will cause the watchdog counter to get reloaded from the preload value and start counting down. If the RTI_INTR_WWD handler does not service the watchdog in time, it could count down all the way to zero and wrap around. No second exception for a time out is generated in this case.
Configuration of DWWD
The DWWD preload value (same as DWD preload) can only be configured when the DWWD counter is disabled. The window size and watchdog reaction to a violation can be configured even after the watchdog has been enabled. Any changes to the window size and watchdog reaction configurations will only take effect after the next servicing of the DWWD.