Sampling POR_B to determine reset type

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Sampling POR_B to determine reset type

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Contributor IV

I'm using SDK 2.6.2 for the MIMXRT1062DVJ6A. How can sample the POR_B input. I want to determine whether someone pressed the reset button so I take appropriate action later. So, if someone presses and holds the reset button (we use the same circuit as the EVK), will the MCU still get reset and run so that can wait, maybe 3 seconds, to see if the reset switch is still being pressed?

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NXP TechSupport
NXP TechSupport

Hello Jeff,

Hope you are doing well.

The POR_B signal is sampled internally by the system reset controller. If the pin is asserted correctly this will cause the chip to be reset automatically. There is no need to take action to properly reset the chip when using the POR_B. Please refer to section 20.7.1.2.1 for the necessary clocks that are used to assert and deassert this pin. In the SRC Reset Status Register you are able to see the reset source. When the system comes out of reset, this register will have bits set corresponding to all the reset sources that occurred during system reset. This register must be cleared by software.

Hope it helps!

Sabina

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Contributor IV

Sabina,

Thanks for the rapid response. What I'm trying to accomplish is a special reset mode where the user has to assert the reset switch for at least three seconds in order to enter a special boot mode. This special mode is rarely needed, so I want to ensure that it is not accidentally entered. I was hoping to sample the POR_B signal for 3 seconds to verify that it is the user's intention to enter the special mode. It is not apparent to me that this is possible, but I need to sure before I try to develop an alternative.

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NXP TechSupport
NXP TechSupport

Hello Jeff,

Thank you for clarifying the intention of your signal. Unfortunately, it will not be possible due to nature of the POR_B in the system reset controller. The external source for the POR_B will initiate the sequence much sooner than 3 seconds, so you will not be able to reach this value. I'd recommend to consider working with a software based interrupt for the special mode that you would like to enter. 

Best Regards,

Sabina

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