Pin 3 of the 555 outputs a regular square wave; you can indeed trigger on any edge. You can also replace the 555 with another source (which would be necessary for more than 2 MHz).
The top transceiver is used only as a transmitter; the bottom transceiver…
Part Number: SN74LV374AT Other Parts Discussed in Thread: SN74LV374A Hi team,
Customer want to know what is the initial status of SN74LV374A when power on. Is Q0 0 or 1?