State of BOOT_MODE pins at Power-Up

[atillametetured]

Greetings,

I need confirmation on a simple subject. If I connect the RESETBMCU of PF0100 to POR_B of i.MX6Q, when all the switching regulators are up and running at the PMIC, it will signal RESETBMCU for 2 to 4 ms. Only in this time interval, regarding the state of the BOOT_MODE[1:0] pins, processor will decided its one of three boot modes, internal boot, serial downloader and boot from fuses.

Thus by adding switches to BOOT_MODE pins, setting the pins to their designated values before the power up, as I give power to the PMIC, the boot mode will be set at the processor and there is no need to do anything else?

An example scenario is;

     BOOT_MODE 1 is pulled to ground, BOOT_MODE 0 is pulled to 3V3, when pmic is powered up and all switching regulators are up, BOOT_MODE is set to 10 which corresponds to Internal Bootmode.

Did I understand this correct?

Regards,

Mete

[igorpadykov · Accepted solution]

Hi Atilla

boot signals are latched some time after POR release, described in

sect.60.6.1.2.3 POR (SRC_POR_B)   i.MX6DQ RM as:

"SRC will prepare the boot information and then de assert mmdc_rst_b."

after system_early_rst_b signal and PLLs locking and generation system root clocks.

Accurate time is not defined.

Recommended to have valid boot signals before POR release.

Best regards

igor

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