Do i need to add a hardware watchdog to prevent software watchdog reset fail?

[everkimage]

Colleague tell me our board need add a hardware watchdog,cause software watchdog in the MCU would be failed to reset the MCU sometimes.

for example,when board meet hard electromagnetic interference.

Do i need to add one?

[dianabatrlova]

Hello,

I'm afraid that hard electromagnetic interference can cause more issues than just the watchdog failure. But this is application dependent.

However, I assume, that you mean the external watchdog.

The useful points were discussed in the community thread below.

https://community.nxp.com/message/816291?commentID=816291 

I'm not sure which MCU you use. If you have a device from MagniV family I recommend you to look at the Hardware Design Guidelines. There is the section "EMI/EMC and ESD Considerations for Layout"

I hope it helps.

Best Regards,

Diana

[everkimage]

Hi Diana,thanks for your reply.

My MCU is MC9S12.

I'm not sure what will make the internal watchdog fail,electromagnetic interference is just an example.

Actually,i wonder under which condition the external watchdog must be used.Why does the internal watchdog fail but external watchdog not?

[dianabatrlova]

Hi,

Unfortunately, I cannot tell you which one is better for you, both of them have advantages and disadvantages. There is no rule where external watchdog must be used.  

It depends on your application requirements on how the highly reliable system is needed.

Best Regards,

Diana