MK02 doesn't reset in VLLS1 when EXTAL is configured as input

Discussion created by k-laus on Apr 26, 2017
Latest reply on May 16, 2017 by k-laus


we're working with a MK02FN64VLH10 and use the internal clocking.


In case of an error, we'll use the vlls1 mode. While in VLLS1 mode, we'll drive a red led (led is set before VLLS1 and in VLLS1 I/O states are held). To restart the microcontroller, we'll drive the reset pin low. Then the red led is turned off (due to the reset, the default pin configuration of the led pin is input) and the microcontroller starts and works well (see: 1. Working reset ).


Now, we've some trouble when configuring the extal Pin (Port A Pin 18 -> PORTA18) as input. Our "normal" resert in VLLS1 mode(drive the reset pin low) doesn't work anymore (see: 2. Don't working reset ). The red led is turned off, but the microcontroller doesn't start anymore.
To start the microcontroller again we have to turn the power supply off and on again (power on reset).
In this state we also haven't any access to the microcontroller by debugging.

The behavior is independent, wether the debugger is connected or not.
We have had a look at the signals at the reset pin and at PORTA18. There are no spikes or anything else we wouldn't expect.


1. Working reset (yellow - reset; green - PORTA18):


2. Don't working reset (yellow - reset; green - PORTA18):


Does anyone have an idea, what we could do wrong?


Thank you very much.