Master sent routing(with address(ID) to get data from slave 1 to 16

Master --at A and B(cables)-->slave(1)
Master---at A and B(cables)-->slave(2)
........
Master---at A and B(cables)--->slave(16)

at the same time
Master --at X and Y(cables) get response from

<---Slave(1)
....
<---Slave(16)

This mean the Master was full duplex and slave(waiting their command response from Master)

Is there someone had .code to doing full duplex(.asm or .C).
clients(MCS-51s) code.

if you look at the above, you will see that there NEVER is traffic in both direations at the same time.
Thus, you are adding a set of transcivers to every board and using cable with two twisted patirs instead of one and gain NOTHING from it.

Erik