iMX RT106x (esp. RT1062) BOOT_CFG pins

[Pencioner]

Hi

I have a question related to BOOT_CFG pins on a custom designed board (in the very beginning of journey). It is planned to boot from a regular NOR QSPI flash and value of all BOOT_CFG pins as 0 is OK (no autoprobe, no special requirements about flash chip freqs and commands/no encrypted XIP etc etc so all zeroes fits well). I know that EVK board uses switched with pull up/down resistors but as i do not need switches at least at this point, would it make problem to leave those pins floating (unconnected)? The corresponding pin's pad configurations are defaulting to 100kOhm pull down so as per my undertanding it should be no problem and it should read as zero on power up. I don't want to use fuses at this stage to keep flexibility if something changes and do not apply irreversible fuse changes to the MCU until design becomes very stable, and i'd like to not add extra components (resistors) at this point as well

Thanks in advance for an advice

[mayliu1 · Accepted solution]

hi @Pencioner 

Thank you for your interest in the NXP MIMXRT product, I would  like to provide service for you.

I really don't recommend  you leave those BOOT_CFG pins floating (unconnected).

1: Floating pins(BOOT_CFG and BOOT_MODE)are highly susceptible to electrical noise in the environment.

2:Without a proper fixed connection, the input state of the pins may become unstable.

Please refer to MIMXRT1060-EVK board design.

Wish it helps you.

BR

mayliu