TMS570LC4357: DWWD causes repeated resets

Hi Andrew,

It is the expected behavior. If you don't feed the dog in the defined window, the watchdog will reset the device. 

Hi QJ Wang,

Thank you for your reply.

I understand that if the watchdog is not fed that the device will reset, but I'm not convinced that this is my problem.

After booting for the first time my test code calls
    dwwdInit( rtiREG1, Generate_Reset, 0, Size_100_Percent );
    dwdCounterEnable( rtiREG1 );

Then it feeds the watchdog for a period of five seconds before it stops feeding it and consequently the device resets as expected.

After the reset the device boots again and I was expecting it to behave in the same way i.e. call dwwdInit() and dwdCounterEnable() and then feed the watchdog for 5 seconds before resetting.

But it doesn't. It resets as soon as it calls dwdCounterEnable( rtiREG1 ).

Does a reset due to a watchdog not put the device into it's initial state?

Is not it possible for the device to recover following a watchdog reset?

Regards,

Andrew

Hi Andrew,

The DWWD expiry time is (DWDPRE+1)*2^13/RTICLK. In your configuration, the DWDPRD=0, assume RTICLK=75MHz, the Texpire=2^13/75MHz=109us. 

So the watchdog has to be serviced within 109us. Otherwise, the NMI or Reset is generated.

Hi QJ,

When running the software on the TMDX570LC43HDK development kit and using the debugger I have noticed that the EXTRST bit in the System Exception Status Register (SYSESR) is not set when the WDRST is set.

I realise that this is not the correct behaviour but, do you have any idea why it would behave in this way?

The consequence of EXTRST not being set when WDRST is set is that getResetSource() returns NO_RESET.

Note that the EXTRST bit is set when the PORST or DBGRST are set.

Regards,

Andrew

Hi Andrew,

The EXTRST bit is set after watchdog reset.

This is the snapshot of my test, the SYSESR=0x2808  --> bit 3 is set

Hi QJ,

In _c_int00() I have a break point on the call to rstSrc = getResetSource() and I run the debugger.
The first time that the break point is hit.

SysEsr is 0x00000808 as shown below.

I then press Resume and my application runs until the Watchdog expires and the break point is hit for a second time.

Now SysEsr is 0x00002800 as shown below. WDRST is set but EXTRST isn't.

I was expecting EXTRST  to be set at this point. Am I correct to expect EXTRST  to be set? If not then why not?

.

I then press Resume again and my application runs for until the Watchdog expires and the break point is hit again.

Now SysEsr is 0x00002000 as shown below. WDRST is set but EXTRST isn't (DBGRST has been cleared by getResetSource()).

If I then restart the debugger, the first time the break point is hit, SysEsr is now 0x00002808.

Why isn't EXTRST set when WDRST is set for the first time?

Why is EXTRST only being set after the debugger has been started?

Thank you.

The EXTRST should be set when WDRST occurs. Did you check the SYSESR value before code enters getResetSource() function?

Hi QJ,

Yes.

My second screenshot above shows the value of SYSESR before the code enters the getResetSource() function.