NMI pin floating

roymessinger · ‎01-21-2018

I'm using K64 on a custom board. Unfortunately, The NMI pin was left floating (in its default state it was connected to a pull down resistor, but this caused the board to not be flashed at all so I left it floating).

I wanted to know the hazards, if any to this situation.

As I've understood there's an internal pull up and also the Flash Configuration Field is at its default state, so both these should cover the situation. Also, the board seems to be working fine.

Am I out of the woods?

mjbcswitzerland · ‎01-21-2018

Roy

A '0' on the NMI line with cause the chip to boot to EzPort mode and thus not work via JTAG.

The internal pull-up "should" keep it at '1' when it boots and avoid this issue and then also avoid any NMI firing once it starts.

If you are worried that the internal pull-up may not be strong enough to always ensure this you can also disable EzPort mode and the NMI pin in the flash configuration so that it can't ever become an issue after initial programming.

Regards

Mark

View solution in original post

mjbcswitzerland · ‎01-21-2018

Roy

A '0' on the NMI line with cause the chip to boot to EzPort mode and thus not work via JTAG.

The internal pull-up "should" keep it at '1' when it boots and avoid this issue and then also avoid any NMI firing once it starts.

If you are worried that the internal pull-up may not be strong enough to always ensure this you can also disable EzPort mode and the NMI pin in the flash configuration so that it can't ever become an issue after initial programming.

Regards

Mark

roymessinger · ‎01-23-2018

Thanks, Mark. As usual, you're a real lifesaver... :smileyhappy: