LG GLOFA-GM Series User Manual page 18

Chapter 2 Definition of terms
the same signal line. Accordingly, RS-422 executes the full-duplex type of communication and RS-485 executes
the half-duplex type of communication.
11) Half Duplex Communication
Two-way communication is available, however simultaneous communication of transmission & receiving isn't
available. This communication type is applied to RS-485 for instance. It is used a lot for multi-drop communication
type which communicates via one signal line by several stations. Half Duplex Communication results from the
transmission characteristic performed by stations one by one not allowing simultaneous transmission by multi
stations due to the data damage of data impact caused by the simultaneous multi-transmission of the stations.
The figure below shows an example of structure based on Half Duplex Communication. Each station in
communication with the terminal as linked with each other can send or receive data via one line so to execute
communication with all stations, where multi-master is advantageously available.
Master station
]
Master station
12) Full Duplex Communication
Two way-communication of simultaneous transmission & receiving is available. This communication type is
applied to RS-232C & RS-422.
Master station
Slave station
Master station
Slave station
Slave station
2-4
Master station
Master station
Slave station