Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 72)

Asynchronous Link Protocols
Chapter 4
4-29
Figure 4.16
Half-Duplex Master Transceiver
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
Receive Yes
No
3
No
Tell Network Layer
Yes
Remove Station
Active
Yes
3
Yes
Duplicate
Yes
No
Create Master Message
Send DLE ACK
11698
DLE EOT Message
OK?
Network Layer
DLE ACK
Timeouts
for this
of Failure
Station
Timeouts
for this Poll?
from Active List
Message
No
No
Network
Layer has
?
No
Yes
?
Message?
?
?
Message to
send?
Send Message
to Destination
Send to
Is Message
for Master
?
Network Layer
Yes
No
Yes No
Send Poll
Station to Poll
Is Master?