Figure A-1:
Typical RS485 Two-Wire Multidrop Network
RS485 Four-Wire Multidrop Network
An RS485 network can also be connected in a four-wire mode. In a four-wire network it’s necessary
that one node be a master node and all others be slaves. The network is connected so that the master
communicates to all slaves and all slaves communicate only with the master. This has advantages in
equipment that uses mixed protocol communications. Since the slave nodes never listen to another
slave’s response to the master, a slave node cannot reply incorrectly.
Manual PCI-COM-1S
20
