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K22/K66 holds reset low when chip is erased and power cycled

Question asked by Corey Wolff on Oct 5, 2017
Latest reply on Oct 6, 2017 by Jorge Antonio Alcala Vazquez

I have been developing code on a K22 micro.  I started with the FRDM-K22 and have moved onto a custom PCB.  During my development, I found that if I erase the flash contents and power cycle the board, the MCU will hold the reset line low indefinitely.  I have multiple debug tools and the only way to 'recover' from this state with a debugger is to use a Segger J-Link to program code back to the device.  Other debug tools see that the micro is in reset and waits for the device to come out of reset.  It will eventually time out since the micro never exits reset.

 

The only other way to get the device to come out of reset in this state is to toggle the EZ Port chip select line, which just puts the micro into EZ Port mode.  Since the board is now out of reset, I can use any of my debuggers to connect and re-program the target.

 

I am able to reproduce this on my K22 custom PCB, a FRDM-K22F and a FRDM-K66F

 

Is this the correct intended behavior?  Is there a workaround (other than toggling the EZP_CS line) to get the MCU out of reset when the flash is blank?

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