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.
Some applications might use a digital watchdog (DWD) integrated in the RTI module. The digital watchdog generates resets after a programmable period, if no correct key sequence is written to the RTI_WDKEY register. Figure 12-251 shows the digital watchdog functional block.
The digital watchdog functionality is implemented such that it can be enabled by software.
The DWD starts counting down from the reset value of the RTI_DWDCNTR (DWD Counter Register). The DWD preload register can be configured at any time by the application according to the desired time-out period.
When enabled by software, the digital watchdog is disabled after system reset. If it should be used, it has to be enabled by writing A98559DAh to the RTI_DWDCTRL register. The DWD timeout period must be configured using the DWD preload register before the DWD is enabled. The DWD cannot be disabled by the application once it is enabled.
When the DWD is enabled by software, any system reset will disable the DWD. This reset could have been generated by the watchdog itself.
If the correct key sequence is written to the RTI_WDKEY register (E51Ah followed by A35Ch), the 25-bit DWD Down Counter is reloaded with the 12-bit preload value stored in RTI_DWDPRLD register. If any incorrect value is written to the RTI_WDKEY register, a watchdog reset will occur immediately. A reset will also be generated, when the DWD Down Counter is decremented to 0.
The user has to take into account that the write to the RTI_WDKEY register takes 3 RTI_ICLK cycles. This needs to be considered for the DWD expiration calculation.
The DWD Down Counter will be decremented with RTI_FCLK frequency. If the RTI_FCLK is switched off via the disable registers of the Clock management, the DWD counter stops decrementing. The DWD module cannot generate a reset under this condition.
The expiration time of the DWD Down Counter can be determined with following equation:
where RTI_DWDPRLD = 0...4095