Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 124)

Full-Duplex Protocol
Chapter 10
10Ć20
Figure 10.12
Message Transfer with Retransmission
Not Full
DLE NAK
OK
xxxx
DLE ENQ
xxxx
SOURCE XMTR LINK RCVR SINK
10049–I
DL
DLE STX xxxx DLE EXT BCC
(Timeout)
??? CK
???
DLE STX xxxx DLE EXT BCC
DLE ACK
(Message Discarded) 1
1 Note that this is detected as a duplicate message.
Figure 10.13 shows a DLE NAK response to the initial message
transmission because the message sink is full. After the message sink is
no longer full, a retransmission of the message causes a DLE ACK
response.