I'm trying to understand EV3 motor TACHO signals circuit on the EV3 hardware schematic.
Please look at the image below.
There are two things I can't understand:
On the left side, the TACHOA0 input is connected to the ADC and Schmitt trigger inputs via RC circuit. I can understand that the 4.7K resistors and 100pF, 47pF capacitors are used to filter the signal. But I can't understand why those two 100K resistors are used.
On the right side, TACHOA1 input is connected to the ADC and Schmitt trigger inputs via RC filter. Here I don't understand the role of MA1 signal.