K64FN1M0VLQ12 MDM-AP detected +CPU status FAILED

[sionp]

Hi,

 I am using MK64FN1M0VLQ12 on a custom board and tried to download an empty main() project with a while(1) loop when I got the debug messages that MDM-AP detected and also CPU status failed. The debug log is attached. After reading through community forums I am a bit confused and also didnt want to brick that MCU on board by playing around with the commands and scripts. Basically my understanding of the security feature in the MCU is also less. Request someone to help to get out of this. We dont need any security in the MCU as of now.

Thanks and Regards,

Sion

[sionp]

The problem has been solved today. There was a reset IC kept on board which when disconnected from the controller the debugger gained control of the controller.Once the disconnection was done I could see a sawtooth waveform on the reset pin of MCU which some one else has also reported seen in their board. But when the debugger was connected the reset went high and then the IDE responded by connecting to the MCU.  I feel that i should have put an open drain reset IC when a debugger is also meant to be used on the board.  Anyhow thanks for those who have gone through my post.

[diego_charles · Accepted solution]

Hello, Sion

Sorry for my late response, but let me say that the information that you provided is actually very useful for the community. Because it deals with the design of reset IC´s for the Kinetis MCU´s.

 As you said an open-drain reset IC its a good choice. As example, the chapter 6.1.4 Digital design of KL82 datasheet provides design considerations for the reset circuitry.

When an external supervisor chip is connected to the RESET_b pin, a series resistor must be used to avoid damaging the supervisor chip or the RESET_b pin, as shown in the following figure. The series resistor value (RS below) must be in the range of 100 Ω to 1 kΩ depending on the external reset chip drive strength. The supervisor chip must have an active high, open-drain output.

Have a great day,
Diego

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