WDT causes reboot loop when underflow occurred once

Question

By default, in my application, WDT is disabled by default and should only be started when instructed to do so by the user. 
 After the WDT is started by a user, the mcu will be reset after an underflow occurs. After resetting the mcu, the mcu constantly restarts. However, the user hasn't enabled the WDT after the reset. 
 The OFS0 register is set as follows:

nd · Accepted Answer

Hello IK 
 Thanks for the reply 
 I reinstaled e2studio and now i can open your project (I normally use IAR). 
 
 We found the problem and the WDT now works as we wanted it to. 
 A bug in our code caused the wdt timer to always refresh on start-up, with the result that we could no longer write to the WDT configuration registers. 
 As long as the user did not give the command to start the WDT then the WDT was off. But as soon as the user started the WDT then it kept running. This was because if an underflow happened and a reset occurred. The WDT stays on but waits to run again until the first time you perform a refresh. By doing this refresh on startup (even before you call the WDT open API) the WDT started running (we don't want this) and that caused another reset due to an underflow and so we got into a loop. 
 Setting the define WDT_CFG_PARAM_CHECKING_ENABLE to 1 helps revealing the problem. 
 Thanks for helping me investigate the problem 
 Kind regards 
 ND

IK_Renesas · Answer

Hello, 
 Thanks for reaching out Renesas Engineering Community! 
 Are you calling in your code the Refresh API to refresh the timer and prevent the counter underflow to prevent the reset? 
 Please, check how this is done in the example provided in the documentation of the r_wdt module. 
 https://renesas.github.io/fsp/group___w_d_t.html#gad64d0778fd0ceccb13a7287bb0d1fca8 
 
 Could you please share with us some sample code to check? 
 
 Best Regards, 
 IK

IK_Renesas · Answer

Hello sir, 
 As far I can understand your request is to be able to choose in your application when the WDT timer will be enabled and a reset will occur. Am I right? 
 I am sorry but from the information you have provided me I cannot understand much to see what is going wrong in your project and the reset due to watchdog underflow occurs even though it is not enabled by the user. 
 However I have created a simple example for you which I think demonstrates what you want to achieve. The example is for RA8D1. 
 Let me provide some details about the example: 
 Here are the configurations for the r_wdt stack added in Stacks Tab:

The example uses other two stacks a GPT timer stack r_gpt and the r_icu stack to trigger an external interrupt every time button S2 is pressed. 
 The timer is configured to overflow every one second and I have set a callback function which occurs every second to refresh the WDT timer counter and prevent the underflow and reset event. 
 If the user presses button S2 an external interrupt will be triggered which will stop the timer, so it will stop refreshing the WDT Timer, which will have as a result the WDT timer to be counting down and as soon as the underflow event occurs a reset due to watchdog will occur. 
 Also in hal_entry function in the beginning of the application I am checking the RSTSR1_b.WDTRF flag to check if it gets value 1 after the reset and see if the reset occurs due to WDT. Also when the reset occurs the red led turns on for a while to indicate that the reset due to watchdog occurred. 
 Check also the printed messages on RTT Viewer for logging: 
 
 So every time I press button S2 the WDT is enabled and reset occurs, as you requested controlled by the user. 
 Something else I would like to mention here is that users generally must be very careful of when they select to refresh the WDT counter to prevent underflow and reset.

Also if for example I set the timer GPT period to a period bigger than the time that it is required to the underflow event to occur on the WDT timer, I also get unexpected resets which are not enabled by the user. 
 
 Find the example below. 
 
 Hope it will help you proceed. 
 wdt_example_RA8D1.zip 
 Best Regards, 
 IK

WDT causes reboot loop when underflow occurred once

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