Boot mode config pins: pull-down on reset?

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Boot mode config pins: pull-down on reset?

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rhu
Contributor I

The boot mode config-pins have pull-down resistors 100k on reset, right?

pastedImage_1.png

So we don't have to put external pull-down resistors, if we want the corresponding bit should be 0.

But, why are on the Evaluation-board pull-ups and pull-down resistors??

pastedImage_2.png

My question: Can/ should/ must I put external Pull-down resistors, if I want the corresponding config bit must be 0?

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FelipeGarcia
NXP TechSupport
NXP TechSupport

Hello René,

 

For BOOT_MODE1 and BOOT_MODE0, use one of these options to achieve logic 0:

 

• Tie to GND through any-value external resistor

• Tie directly to GND

 

A value of 4.7 kohm is preferred for high-noise environments.

 

For further information I highly recommend you to check the i.MX RT Hardware Development Guide for the MIMXRT1050/MIMXRT1060 Processor.

 

Hope it helps!

 

Best regards,

Felipe

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rhu
Contributor I

...and what about the BOOT OPTIONS Pin values on GPIO_B0_04/05.../15?? Again my question: Can/ should/ must I put external Pull-down resistors, if I want the corresponding config bit (also on GPIO_B0_04 etc.) must be 0?

Best regards

Rene

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FelipeGarcia
NXP TechSupport
NXP TechSupport

You can take same recommendations for those pins as well. External resistors are recommended to avoid noise and uncertainty of signal state on boot pins during reset process.

 

Regards,

Felipe

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rhu
Contributor I

Hi Felipe,

I understand: it's recommended to put external resistors in case of noise.

but if I understand this correct:

pastedImage_1.png

pastedImage_2.png

For example: GPIO_B0_04 has internal 100k pull-down on reset state. So this would be read as '0' after reset, if there is not to much noise, and the desired boot mode configuration is set.

I think, that's the reason for these pull-down resistors on reset state, that you don't have to put a lot of external resistors, if you just want this pin on Low-Level after Reset, right?

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FelipeGarcia
NXP TechSupport
NXP TechSupport

Hi René,

 

Please check the below note from Hardware Development Guide.

The BT_CFG[] signals are required for a proper functionality and operation and shall not be left floating during development if BT_CFG[] fuses and BT_FUSE_SEL are not configured.

Regards,

Felipe

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