hi,
referring to Andy's 'lower' picture ...
in order to get the right answer from a slave(n),I have to check the the transmission coming from the master(working in mode 3 multip.)So my 'sniffer' will have on its RX pin the message(n) from the master and immediately after it needs to read the answer of the slave (n).So there must be a commutation for the two transmission lines (master TX and slave TX (n)--> RX).
This is the only way i found to 'synchronize' with a certain slave (n).
Will a cd4066 be OK to switch or 'and' gates are preferrable? Will this commutation introduce noise problems?
any other solution?

Ed