Why PTA4 LED in KL34 is ON by default and has 1v?

[abosamy]

I use KL34 on my costume board. The problem is that once I connect it with power, the LED on PTA4 becomes ON. When I measured the voltage on it, It's 1v.

Why is this pin ON and why it's value is 1v?

[kerryzhou]

Hi Abo Samy,

    PTA4 is the NMI pin,  this is the input pin, not the output pin.

    If you want to use the GPIO to control the LED, please choose another pin, NMI is the Non maskable interrupt pin, you should add an 4.7K to 10K external pullup resistor in this pin.

Wish it helps you!

Have a great day,
Jingjing

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