MCU monitoring

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jharvey
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MCU monitoring

Post by jharvey »

I figured we should bring up this monitoring thing. I believe the MCU has on-board watch dog and brown out, but what about other features. I see SECU3 uses this interesting Maxim DS1811-15 chip. It delays 150ms before passing power to the MCU, allowing the power supply to solidify before powering up fully. Are there thoughts, concerns, or other ideas relative to MCU monitoring?
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nitrousnrg
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Re: MCU monitoring

Post by nitrousnrg »

In my (quite personal) opinion, a good design doesn't need a watchdog timer.

About the brown out, I don't see it in the datasheet. The MCU has power-on reset based on the voltage seen in the reset pin, though. Keep in mind that if the cpu is constantly powered, the power supply transient happens once in a while. And if you see an out-of-tolerance power supply condition during normal operation, I wouldn't like to have the cpu irremediably dead for 150ms, I prefer the power-on reset behavior.

The power-on 150ms could be obtained from an RC circuit connected to the reset pin, so the pin is held in '0' until the capacitor gets charged.

What I like about it is that it is very small and easy to put in any design.
Marcos
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Fred
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Re: MCU monitoring

Post by Fred »

+1 marcos, however there is no harm in implementing a watchdog/COP monitor. I intend to eventually. I initially thought it had to be within a window, and didn't like that, but you can just have it setup for "before X ms" which is fine. One day, after everything else. It costs nothing to have it there.
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Fred
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Re: MCU monitoring

Post by Fred »

+1 means NO way for 150ms
+1 means good design = cop unrequired

However, I think there is a brown out ISR. I've used it and posted about it.

Fred.
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