Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 56)

4–2 Using Full-duplex Protocol to Send and Receive Messages
Publication 1770Ć6.5.16 - October 1996
With full-duplex protocol, a link uses two physical circuits for
two-way simultaneous message transmission (command or reply
message packets). These two physical circuits provide
communication on four logical paths:
Figure 4.1
Data paths for twoĆway simultaneous operation
path 1
path 2
path 3
path 4
receiver B transmitter A
transmitter B receiver A
circuit 1
circuit 2
• On the first circuit, transmitter A sends messages to receiver B (path 1) and receiver A sends response
control symbols (DLE ACK, DLE NAK) to transmitter B (path 3).
• On the second circuit, transmitter B sends messages to receiver A (path 4) and receiver B sends
response control symbols (DLE ACK, DLE NAK) to transmitter A (path 2).
• All message and symbols on the first circuit are traveling in the same direction (node A to node B) and all
messages and symbols on the second circuit are traveling in the opposite direction (B to A).
FullĆduplex Protocol
Message Transmission