OpenRex schematic

[justaelvis]

Hi Robert,
I am confusing with the reverse schottky diode in the Open Rex schmatic. Could you explain the function of those diode in both cases for me. Thank you very much!

[robertferanec]

The first picture: If U16 output is High we do not want any currents to flow to the circuit behind the diode (so even if signal behind diode is LOW and U16 output is HIGH, the currents will not flow there - there will be no "short circuit" between High and Low). However, if U16 output is LOW, we would like this level to be transferred to the circuit behind the diode. You need to be careful when using this kind of circuits - you need to use diodes or open drain / open collector circuits / gates if diode is not used.

Similar on the second picture. If POR is low, RGMMIII_RSTn will be also low (system reset will reset all peripherals, including ethernet), however, if POR is high, you still can control RGMMIII_RSTn (so if your board is running and for some reason you need to reset Ethernet, you still can pull it LOW) without influencing POR (without reseting the whole board).

[justaelvis]

Thank you Robert. I am fully understand it now