Boot mode config pins: pull-down on reset?

[rhu]

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

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??

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

[FelipeGarcia]

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]

...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

[FelipeGarcia]

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

[rhu]

Hi Felipe,

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

but if I understand this correct:

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?

[FelipeGarcia]

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