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I have a Microcontroller - S32K116 - 48 Pin IC. - Datasheet - Reference Manual

I have a Voltage divider (for input voltage monitoring purpose) connected to the Pin 16 (PTC3) of the Microcontroller.

Image :

enter image description here

I have NOT programmed my Microcontroller. But I have connected this Voltage divider circuit to the PTC3 pin of the Microcontroller in my board.

If I give 5V input to the Microcontroller and the same 5V for the Voltage divider, If I measure the output of the voltage divider, I am getting like 0.7V to 0.8V. I should actually get a output voltage of 2.5V, for input voltage of 5V, right?

But then I realized that since my Microcontroller is not programmed, there must be something to do with the default state of the pins (does default state means before programming the microcontroller or after releasing the reset of the microcontroller?) of the microcontroller.

I checked the Reference manual of the Microcontroller.

Note 1 :

On page 89 of the reference manual, table 4.3, it is mentioned as for "Other pins" - the default state is "High Impedance".

Note 2 :

On page 91 of the reference manual, there's a paragraph mentioning - "By default, ALT0 mode (configured by PTXn_PCR[SSS] as 3’b000) corresponds to disabled functionality and pad represents disabled (highimpedance) state. In case if the pad consists of analog functions, the ALT0 mode corresponds to analog functionality once the analog module is configured to enable corresponding channel/input."

My questions :

  1. From the Note 1, can somehow like provide me a small illustration of what the "High Impedance" state of the Microcontroller pin would actually look like? (I understand that in High Impedance state, there is no current draw, but just want to know how the impedance state of the microcontroller pin would look like)

  2. In the sheet, S32K116_IO_Signal_Description_Input_Multiplexing", I found like

enter image description here

I am not able to link this table with the Note 2 - paragraph which I have mentioned above.

a. What does default state actually mean? Is the state before the microcontroller is programmed? Or is the state after the microcontroller (once after programmed) Reset is released? What does the default state mean in this context and what does the ALT0 mode indicate? Since, my PTC3 is an analog pin, what is the paragraph in Note 2 trying to convey?

  1. Why am I getting 0.7V or 0.8V instead of the required 2.5V when my Microcontroller is not programmed?
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  • \$\begingroup\$ You haven't programmed the MCU. This doesn't mean the MCU hasn't been programmed. The manufacturer might have uploaded a demo program that uses the PTC3 pin. \$\endgroup\$
    – Codo
    Aug 6, 2020 at 7:01
  • \$\begingroup\$ Thank you. In that case, as per that spreadsheet, what would be the default state of the PTC3 pin ? And what do you mean by, or like why do you call it the default state when the controller has been already programmed? \$\endgroup\$
    – user220456
    Aug 6, 2020 at 8:48
  • \$\begingroup\$ If the manufacturer has uploaded a program, the PTC3 pin might have been configured in any state. You can't know what it is. Upload your own simple program that doesn't configure PTC3 and then you are sure it is in its default state and hasn't been configured otherwise. \$\endgroup\$
    – Codo
    Aug 6, 2020 at 9:10

1 Answer 1

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What does "High Impedance" state of a pad look like?

Output driver, off.
Input receiver, off.
pull logic, off.
ADC channel selection, off.
All you have are the diodes.

enter image description here enter image description here

What does default state actually mean?

The state set at reset (falling edge on reset pin) until changed by software (eg: your software of bootloader) The ALT columns refers to other options the you can activate on the multiplexer behind do and ind.

Why am I getting 0.7V or 0.8V instead of the required 2.5V when my Microcontroller is not programmed?

There is circuitry on the board you are missing. The leakage on pins is only max 0.5 uA, which would be the equivalent of a 10 M ohm load on your divider.

Or the part isn't as empty as you think.
Or, you have destroyed the pad by ESD strike.

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  • \$\begingroup\$ Thank you for your answer. Isn't the leakage current on the pins 5uA (5V/1Mohm)? And I am sure that I have not destroyed the pads due to ESD as I maintained proper precautions. So, you mean, the default state is the state of the pins during RESET? Isn't that state actually the RESET state? I am sorry. I get confused. Please provide a little more clarity of what is the Default state and how to get into it? \$\endgroup\$
    – user220456
    Aug 6, 2020 at 8:52
  • \$\begingroup\$ I understand even if the Controller isn't loaded with my software program, there is already a bootcode given by the manufacturer from the factory. So, is the default state - the state only having the bootcode (coming directly from the factory) or is it the state after the RESET is disabled? \$\endgroup\$
    – user220456
    Aug 6, 2020 at 8:54
  • \$\begingroup\$ @Newbie I don't think this part has a ROM bootloader. So the bootcode does not change pin states. They will remain in default state set since falling edge on reset pin until reset is lifted and software changes it. Please consider other board leakage or esd damage. \$\endgroup\$
    – Jeroen3
    Aug 6, 2020 at 9:19
  • \$\begingroup\$ Thank you for the answer and comment. So, Default state is the state when the RESET (active low) is active right? So, Default state and RESET state both are the same? \$\endgroup\$
    – user220456
    Aug 6, 2020 at 16:00

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