KE06 NMI pull-up

[davidsherman]

I'm trying to solve a little mystery.  The pin PTB4 is also the /NMI pin.  On reset, the internal pull-up is disabled in the PORT_PUE0 register.  On the FRDM-KE06 board, there does not appear to be a pull up resistor in the schematic, and I can't find one on the board.  There appears to be some pull-up somewhere, because I can measure 3 volts on the pin on the Freedom board.  So, is there some pull up that's on by default, or is there a resistor on the schematic that I'm not seeing?  In short, can the pin be left disconnected as it appears to be on the Freedom board, or does it need to have a pull-up resistor supplied?

[davidsherman]

Ah, thank you!  I had missed it in that part.

[Paul_Tian · Accepted solution]

Hi, David

In KE06 reference manual, you can find

NMI Pin Enable

This write-once field can be written after any reset. When NMIE is set, the PTB4/KBI0_P12/FTM2_CH4/SPI0_MISO/ACMP1_IN2/NMI pin functions as NMI.This pin defaults to NMI following an MCU POR. Other resets will not affect this bit. When NMIE is set, an internal pullup device on NMI is enabled. And this bit default value is 1. So this pin has internal pull-up resistor.

Hope my reply can help you.

Best Regards

Paul