Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 122)

Full-Duplex Protocol
Chapter 10
10Ć18
Figure 10.10 shows a DLE NAK response to the initial message
transmission. After the message is retransmitted, a DLE ACK response is
given.
Figure 10.10
Message Transfer with NAK
Not Full
DLE ACK
OK
xxxx
DLE STX xxxx DLE ETX BCC
xxxx
SOURCE XMTR LINK RCVR SINK
10047–I
DLE NAK
DLE STX x??x DLE EXT BCC
Figure 10.11 shows the transmitting station sending a DLE ENQ sequence
after a timeout because it did not receive the initial DLE ACK response.