Unused port pins on Kinetis microcontrollers

[vijenad]

Microcontroller Part # : S9KEAZN16AMLC

Code Warrior :  Version: 10.6.4

Using Processor Expert

There are few unused microcontroller port pins in our project, do we need to configure these pins to input/output  in the software or can we leave those pins without any configuration?

In the hardware, is it necessary to pull-up or pull-down the unused pins?

[david_diaz]

Hello,

About unused pin of Kinetis E Series, I have below suggestion:

Unused I/O do not need to connect anything (i.e. float) and set it as output logic low. The floating port pins are not allowed in some applications, I suggest to add 10K ohm pull-down resistor connecting to the unused pin. Don’t try to connect any unused I/O to power or ground directly.

I hope this information will be useful for you.

If I misunderstood your question, feel free to let me know.  I will be glad to help.

Have a great day.

David Diaz.

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[vijenad]

Thanks David,

1. 10 K ohm pull-down resistor is required only depending on the application - am I correct?  If our application allows for floating port pins then we can go with floating pins, as the concern is raise in BOM cost and PCB space.

2. If there are floating port pins then - What are the possible consequences at application level ? (I agree, it depends on our application, but if there are any references, then it may be helpful)

3. We are using processor expert, it allows to configure port pin as output, but we are not sure - how to set it logic low.

[david_diaz]

Hello Vijeendra N,

I have to personally apologize for the long delay it took to come back to you.

In this case, do not connect unused I/O pins to anything. Make it floating, and then set it as output low in software. Periodically refresh the state of the pin to avoid changes in state by noise. If floating pins are not allowed in a particular application, connect a 10kΩ pulldown resistor for each unused pin. Do not connect any unused I/O pin to power or ground directly.

I hope this information will be useful for you.

If I misunderstood your question, feel free to let me know.  I will be glad to help.

Have a great day.

David Diaz.