Is an external pulldown resistor absolutely necessary on each pin of the BT_CFG[] pins?

[Taka05]

Setting the MIMXRT1062's BOOT_MODE[1:0] to Internal Boot and booting with the BT_CFG[11:0] set to all "0", is an external resistor absolutely necessary?

Since the internal pullup/down is not changed from the RESET state (pulldown 100Kohm), could this internal resistor be effective?

[Omar_Anguiano · Accepted solution]

Hello

I hope you are well.

Yes, it is necessary to add external termination to those pins to avoid incorrect settings caused by other factors like noisy environments.
If you want to avoid using Boot_CFG pins, then you can use boot from fuses configuration, in that way the bootloader takes boot configuration from the fuses instead; leaving boot_cfg pins available for other functions.
Before using this setting you need to be completely sure of your configuration since fuses cannot be overwritten.

Boot_Mode pins cannot be replaced so even if you use fuse settings you still need to have available boot_mode pins.

Boot_Mode is configured in Boot From Fuses (b00)

- BT_FUSE_SEL = 0, No application in boot device, BootROM enters serial downloader mode                -BT_FUSE_SEL = 1, valid application in boot device, BootROM gets all boot device info from fuse

Boot_Mode is configured in Internal Boot (b10)

- BT_FUSE_SEL = 0, valid application in boot device, BootROM gets boot device info from boot_cfg pins.
-BT_FUSE_SEL = 1, valid application in boot device, BootROM gets all boot device info from fuse.

Best regards,
Omar