GPIO Pin's State on power-up

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GPIO Pin's State on power-up

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eduardrazumovsk
Contributor III

Hello,

I'm designing a system with K64 MCU

My question regarding all GPIO's state on power-up :

1. The GPIO's state on boot is output or input ? if so, is it PU/PD/HiZ ?

2. What doe's it mean that the default function of a GPIOs is "DISABLED" ?

Looking at the reference manual - http://cache.freescale.com/files/microcontrollers/doc/ref_manual/K64P144M120SF5RM.pdf

Page 244, chapter 10.2.2 Port control and interrupt summary

"Pull enable at reset - Disabled" - so i can understand from that that the GPIO is defined as Input Hi-Z ?

Please clarify this issue for me

Thanks & Regards

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3 Replies

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Jorge_Gonzalez
NXP Employee
NXP Employee

Hello Eduard Razumovsky:

Mark's response is completely correct. You should look at the Default column in the pinout table.

DISABLED indicates no function after reset, so that is High-Impedance.

Pins with an analog MUX option will be connected by default after reset to their corresponding analog module.

Regards!

Jorge Gonzalez

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gschelotto
Contributor V

Okay, but what about this case on my MK02Z?

powering up issue on MKE02Z GPIO

On power-up PTB4 seems to follow the VCC ramp and after PE initialization this is set as a digital output with zero value.

regards,

gaston

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mjbcswitzerland
Specialist V

Hi

No pins are GPIOs outputs after reset.

If their pull-up is disabled at reset it means that there is no pull-up or pull-down connected. [Only the pins that default to JTAg use have pull-ups or downs eabled out of reset].

Some pins default to peripheral functions (see 10.3.1) and not GPIO.

If disabled out of reset, it means that there is no connected default function - the pin is not GPIO input without first setting the GPIO Mux function (Alt 1).

Regards

Mark

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