The Pro Mini, like some early Arduino models, just has a current limiting resistor and an LED between Pin 13 and Ground. The UNO and MEGA models put a op-amp between Pin 13 and the LED so they don't put any significant load on the pin.
The Pro Mini, like some early Arduino models, just has a current limiting resistor and an LED between Pin 13 and Ground. The UNO and MEGA models put a op-amp between Pin 13 and the LED so they don't put any significant load on the pin.