S, Erik Christiansen piše: > On Sun, Dec 05, 2010 at 01:40:58AM -0800, Kirk Wallace wrote: >> On Sun, 2010-12-05 at 09:44 +0200, Slavko Kocjancic wrote: >> ... snip >>> That's funn... If you already have watchdog (hardware) to keep ATtiny >>> RESET good why do you need that MCU at all?!? Seems nonsense for me. >> I think because the MCU is used to validate EMC2 before powering up the >> dangerous bits of the machine. The MCU's internal watchdog validates the >> MCU itself(?), which is a separate function. I need to read the MCU >> manual to see what features come with the using the watchdog. I suppose >> EMC2 could be used to validate the MCU, but things are getting >> complicated. > Hmmm, its seems Slavko read right past "microcontroller's on-board > watchdog" in my post. :-) > > Yes, the ATtiny's watchdog is on-chip, so the quandary doesn't arise. > I wouldn't trust a microcontroller in any critical role, without a > hardware supervisor. On an AVR, it has it's own clock, so even if the CPU > clock dies, the watchdog reset will tri-state port pins. > > That is why a pull-[up|down] to a safe state is helpful on a port pin. > It takes over in reset scenarios. > > The watchdog improves the reliability of the microcontroller by > providing recovery from soft errors, whether caused by extreme > transients or alpha particles. > > However, the ATtiny's watchdog is best enabled only after its program > has been debugged. ;-) > > Erik > > I use that MCU's And can tell you that Watchdog on tiny controlers are good one. But have problems. The mcu itself MUST be started correctly (reseted) and after that watchdog work correctly. But when big machine starts (with a lot of solenoids) the proper reset is wery hard to realize! And belive me that if you think in a way that unproper reset may casuse injury then just stay off that.
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