long distance communication with support of addressing

Hello I need a idea how to send data of multiple arduino boards to "master" also arduino.

requirements :
20 SLAVES
bi directional communication
addressing "slaves"
long distance, about 100m
few wires, 10 MAX.

Only STANDART I have found that will work over 100m is rs-485 but I cant find how to address the slaves and get the info out of them.

I want to send 3bit FROM SLAVE TO MASTER, WHEN MASTER REQUIRE INFO FROM SLAVE example 001 or 111.

So my Master arduino can over serial print out some thing like this:

SLAVE1 000
SLAVE2 010
SLAVE3 111....

I have no example code because I have no hardware "max-485 " so I didnt experiment.

If I wrote something wrong please correct me.
any help and idea is welcome.
sorry for bad english.

check - Gammon Forum : Electronics : Microprocessors : RS485 communications