So on the Atmega328 datasheet there is a comment on the "Internal Pull-Up Resistor" being set to "on". It specifically says this:
Pxn will source current if ext. pulled low.
Maybe im just being really stupid....but what does this mean? I mean I understand what a Pull-Up does....but then it's talking about externally being pulled low? Im assuming this is saying that if the Pin is pulled up, it's connected to VCC (in some way, im probably wrong) but that if we connect the outside pin to GND that we'll have current flowing from VCC--->PIN--->Ext. Pull-down resistor---->GND.
Maybe im mis-understanding "Why" it's saying this? I assume because you'll just be wasting power?