Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 38)

Chapter
3
Publication 1770Ć6.5.16 - October 1996
Using HalfĆduplex Protocols to
Send and Receive Messages
In half-duplex protocol, devices share the same data circuits,
therefore only one device can “talk” at a time. Half-duplex protocol
can be likened to a one-lane bridge: each car must wait its turn to
cross the bridge. (To compare half-duplex to full-duplex protocol,
refer to Chapter 4, “Using Full-duplex Protocols to Send and
Receive Messages.”)
Read this chapter to help learn how to use half-duplex protocol to
send and receive messages. It contains these sections:
Section Page
HalfĆduplex Protocol Message Transmission 3-2
Transmitter and Receiver Message Transfer 3-3
HalfĆduplex Protocol Environment 3-3
Message Characteristics 3-7
Master Polling Responsibilities 3-7
Slave Transceiver Actions 3-9
HalfĆduplex Protocol Diagrams 3-11