This is for interfacing with the Teensy 4.0.
Top circuit is for reading the IE bus. Push button simulating IE bus traffic at +5 volts (avg 2.5v, with peaks at 5v). Voltage out is 2.38v peak. Because of the nature of the traffic (on/off rapidly), to most multimeters it will average at 2.5v.
Bottom circuit simulates writing to IE bus. Must be within timing spec, which is 20 us for HIGH pulses and 32 us for LOW pulses. Essentially using a 3904 transistor as an open collector. This out line is always pulled high, so the code will always pull the line low to write to it.
