Chapter 6
drivers to Node 0’s receiver. All of the secondary nodes monitor messages from
Node 0. The node being addressed replies on the other pair of wires. The
advantage is that the secondary nodes don’t see the other nodes’ replies. With a
single data path, all of the secondary nodes receive all of the network traffic.0
Many RS-485 circuits are half-duplex, where multiple drivers and receivers
share a signal path. The interfaces form a serial network, and each computer
with an RS-485 interface is a node in the network.
Networks typically use half duplex interfaces and allow one node at a time to
transmit. Links with just two devices can be half duplex as well. Microcontrol-
lers that allow configuring a port bit as input or output can send and receive on
a single port bit, reconfiguring the bit as needed. You might use this approach if
you need to use the fewest number of port pins or wires possible. If you need to
transmit in just one direction (simplex), you of course need only one data path.Figure 6-7: A full-duplex RS-485 circuit provides a data path for each direction..Figure 6-8: In this full-duplex, multi-node circuit, Node 0 transmits to all other nodes
on one line and receives from all other nodes on the other line.