Re: Can I noise hang a ColdFire forever...?

Dear Joshua
...Why doesn't the relay have a freewheeling diode or some other means of suppression? ...
This diode ausence is not a design specification, just a way to experience the ColdFire protectios x EMI, besdes superficially evaluate the target if installed in a not clear enviroment. I mean, exactly because I want to generate a EMI disturb.
At the begining of this discussion I was very tended to use external watchdog, but now I´m think that the only way to guarantee  the ColdFire doesn´t  hang  (considering it has not get damaged) is by using external watchdog.
I experienced many many 8 bits designs, and I conclude that this machines reached a very good level of protection against this kind of situation, I mean, not that they don´t reset, but they don´t hang, including many Freescale devices...
I got a bit disappointed with it...  I thought this subject was already "robustly" solved, considering ColdFires are a reasonable year old devices...but ...lets face it as it ...
Very thanks for your attention Joshua


  ----- Original Message ----- 
  From: Vantol, Joshua 
  To: Ricardo 
  Sent: Friday, March 07, 2008 11:03 AM
  Subject: RE: [ColdFire] Can I noise hang a ColdFire forever...?


  Ricardo,

  Why doesn't the relay have a freewheeling diode or some other means of suppression? You do risk causing electrical overstress and permanently destroying the processor, so, while the watchdog not clearing the fault is a problem, you absolutely do need to fix this problem at the hardware level.

  Now, as far as the watchdog goes, the watchdog on the 5213 isn't all that great. It doesn't generate a true reset, but rather vectors to a "watchdog reset" vector. If things are really messed up, it's likely that won't work. Early versions of the reference manual offered that you could configure the watchdog to generate a reset, however, it was found that this didn't always work right, and so reference to this mode was removed from the reference manual. 

  An external watchdog would be a great idea. There are some pretty good ones out there. Even a few that are integrated with a voltage regulator.



------------------------------------------------------------------------------
  From: [email protected] [mailto:[email protected]] On Behalf Of Ricardo Raupp
  Sent: Thursday, March 06, 2008 5:21 PM
  To: Vantol, Joshua
  Subject: [ColdFire] Can I noise hang a ColdFire forever...?


  Hi people
  I´m using a 5213 target and it hangs up after a turn off a close 12V/35mA relay wich doesn´t have freewheling diode, that is, generating a noise.
  I´m using watchdog and others interrupts in order to make it resets, but "sometimes" it is not enought, the cpu
  simply stops and only by a hw reset it turns to work back.
  I´m not concerned about the reset issue,but about the hang forever detail....reset after noise is acceptable e expectaed, but hang up ...never...:(:( ??
  My question:
  - Is ColdFire able to "allways" reset after a disturb (conducted or induced)?or should I use a external watchdog?Some special care to assure reset allways?
  Thanks
  Ricardo Raupp

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