topic K70 reset pin state in Kinetis Microcontrollers

K70 reset pin state

stephenchorlton — Thu, 02 Jul 2015 08:09:26 GMT

On the K70 when a watchdog reset occurs the state of the RESET_b pin does not change.

Is this correct?

The manual implies that it should go low when a watchdog reset occurs.

Re: K70 reset pin state

Jorge_Gonzalez — Fri, 03 Jul 2015 00:28:38 GMT

Hello Stephen Chorlton:

The Reset_b pin is expected to assert (change from high to low) with a watchdog reset. I took the next scope image from a TWR-K70F120M constantly resetting by the watchdog:

Are you using a custom board? Can you show the schematics for the Reset_b pin connection?

Regards!,
Jorge Gonzalez

Re: K70 reset pin state

stephenchorlton — Mon, 06 Jul 2015 13:02:55 GMT

Hi Jorge,

Thanks for the prompt reply.

I have some more information regarding our problem.

We do see a pulse on the Reset_b pin when I deliberately cause a reset via the watchdog.

The problem we have is if the clock source to the K70 fails. Clock is sourced from an external phy chip.

This causes the watchdog to go off (watchdog clocked by LPO), but we do not see a pulse on the Reset_b line.

Is the reset pulse driven by the input clock?

The underlying problem is that we require the reset pulse to reset the phy chip and restart the clock.

Regards,

Steve

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