I am following a schematic about a one-way logic 3.3->2.8 level shifting circuit.
The hardware in question is a MCU output that drives 3.3V and the input of the UART interface of a SIM800 GSM Module. Im trying to simulate the circuit but can't figure out why it's supposed to work connected as it is. The Hardware design document of the input module doesnt specify what kind of input it is. And gives other circuits as recomendation:
The specific questions are why do the circuits work like this? How can I emulate the internal components to simulate and check the proper behaviour?