Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 137)

Half-Duplex Protocol
Chapter 11
11Ć10
Figure 11.3
Implementation of Half-Duplex Protocol
XCVR
Select Station
Poll Selected Station
Start Timeout
Receive
No Receive Yes
Message
No
No Yes
Yes
Set Active Station Flag
Get Message from
Send Message
Start Timeout
Received Yes
No
3
No
Tell Network Layer
Yes
Remove Station
Active
Yes
3
Yes
Duplicate
Yes
No
Give Message
Send DLE ACK
10053–I
DLE EOT Message
OK?
Network Layer
DLE ACK
Timeouts
for this
of Failure
Station
Timeouts
for this
from Active List
Message
to Network Layer
No
No
Network
Layer has
?
No
Yes
?
Message?
?
Poll?
?
Message to
send?