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WDOG unlock causes reset

Question asked by biafra on Mar 14, 2018
Latest reply on Aug 2, 2019 by biafra

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Hi everyone,

I'm having trouble on configuring WDOG.

I'm using a custom board based on MK66, MCUXpresso 10.1.1 and SDK 2.3.

I need to use the WDOG timer: since it is disabled in the startup function SystemInit(), I need to enabled it at the beginning of my program (after hardware init):

WDOG_GetDefaultConfig( &WdogConfig );
WdogConfig.clockSource = kWDOG_AlternateClockSource;
WdogConfig.prescaler = kWDOG_ClockPrescalerDivide5;
WdogConfig.workMode.enableStop = true;
WdogConfig.timeoutValue = WDOG_TIMEOUT_VAL;
WDOG_Init( WDOG, &WdogConfig );

I step the program through WDOG_Init() -> WDOG_Unlock(): reset occurs at the first instruction of the unlocking sequence:

base->UNLOCK = WDOG_FIRST_WORD_OF_UNLOCK;

The ALLOWUPDATE bit in the STCTRLH register is set (by the SystemInit() function), the WDOG bit in SRS0 register is set (indicating the reset cause is the WDOG timer) and the RSTCNT register increments every reset.

I've no idea, what can I check?

Many thanks

Biafra

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Jing Pan

Mar 16, 2018 1:22 AM

Hi Biafra,

The watchdog issues a reset, that is, interrupt-then-reset if enabled, to the system for any of these invalid unlock sequences:

• Write any value other than 0xC520 or 0xD928 to the unlock register.
• ALLOW_UPDATE is set and a gap of more than 20 bus clock cycles is inserted between the writing of the unlock sequence values.

So don't follow the code step by step. This will cause a reset.

Regards,

Jing

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biafra @ Jing Pan on Mar 16, 2018 2:12 AM

Hi Jing,

I stepped into the code because the processor resets.

If I step over (F6 button) the WDOG_Init() function or run, the processor resets. The WDOG_Init() function is the SDK one with no changes: it disables the interrupts before the unlocking sequence and it enables them back at the end of configuration.

Is there something else to verify?

Many thanks

Biafra

2 people found this helpful

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Jing Pan

@ biafra on Mar 16, 2018 3:03 AM

Hi,

I made a example. It works fine.

Regards,

jing

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frdmk22f_driver_example_wdog.zip616.4 KB

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biafra @ Jing Pan on Aug 2, 2019 8:49 AM

Hi Jing Pan,

This thread is old, this year the project changed and didn't need the watchdog anymore, but I started a new project and the problem came again.

In the new project I'm using a custom board based on MK66, MCUXpresso 11.0.0 and SDK 2.6 and Freertos 10.2.0.

I've made some further tests and I have some news: if I use the main function of your project, WDOG_Init() is executed with no problem. So I inserted the wdog init in different position of my code: it works until WDOG_Init() is called before the os start, but it doesn't work it's called at the beginning of the first task.

------------------------ This example works -------------------------------

void main( void )

{

...

xTaskCreate( ... ); //create first task

InitWDOG(); //init wdog

vTaskStartScheduler();

}

------------------------------------------------------------------------------------

------------------------ This example doesn't work -------------------------------

void main( void )

{

...

xTaskCreate( ... ); //create first task

vTaskStartScheduler();

}

void FirstTask( void * )

{

InitWDOG(); //init wdog

...

}

------------------------------------------------------------------------------------

Do you have any advice to test?

Many thanks

Biafra

2 people found this helpful

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4 Replies

Jing Pan Mar 16, 2018 1:22 AM
Mark Correct
Correct Answer
Hi Biafra,
The watchdog issues a reset, that is, interrupt-then-reset if enabled, to the system for any of these invalid unlock sequences:
• Write any value other than 0xC520 or 0xD928 to the unlock register.
• ALLOW_UPDATE is set and a gap of more than 20 bus clock cycles is inserted between the writing of the unlock sequence values.
So don't follow the code step by step. This will cause a reset.

Regards,
Jing
1 person found this helpful
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- biafra @ Jing Pan on Mar 16, 2018 2:12 AM
  Mark Correct
  Correct Answer
  Hi Jing,
  
  I stepped into the code because the processor resets.
  If I step over (F6 button) the WDOG_Init() function or run, the processor resets. The WDOG_Init() function is the SDK one with no changes: it disables the interrupts before the unlocking sequence and it enables them back at the end of configuration.
  
  Is there something else to verify?
  
  Many thanks
  Biafra
  2 people found this helpful
  Like • Show 2 Likes2
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  - Jing Pan @ biafra on Mar 16, 2018 3:03 AM
    Mark Correct
    Correct Answer
    Hi,
    I made a example. It works fine.
    
    Regards,
    jing
    Attachments
    frdmk22f_driver_example_wdog.zip616.4 KB
    1 person found this helpful
    Like • Show 1 Like1
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    - biafra @ Jing Pan on Aug 2, 2019 8:49 AM
      Mark Correct
      Correct Answer
      Hi Jing Pan,
      
      This thread is old, this year the project changed and didn't need the watchdog anymore, but I started a new project and the problem came again.
      
      In the new project I'm using a custom board based on MK66, MCUXpresso 11.0.0 and SDK 2.6 and Freertos 10.2.0.
      
      I've made some further tests and I have some news: if I use the main function of your project, WDOG_Init() is executed with no problem. So I inserted the wdog init in different position of my code: it works until WDOG_Init() is called before the os start, but it doesn't work it's called at the beginning of the first task.
      
      ------------------------ This example works -------------------------------
      void main( void )
      {
         ...
         xTaskCreate( ... ); //create first task
         InitWDOG(); //init wdog
         vTaskStartScheduler();
      }
      ------------------------------------------------------------------------------------
      
      ------------------------ This example doesn't work -------------------------------
      void main( void )
      {
         ...
         xTaskCreate( ... ); //create first task
         vTaskStartScheduler();
      }
      
      void FirstTask( void * )
      {
         InitWDOG(); //init wdog
         ...
      }
      ------------------------------------------------------------------------------------
      
      Do you have any advice to test?
      
      Many thanks
      Biafra
      2 people found this helpful
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WDOG unlock causes reset

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