Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 71)

4–17 Using Full-duplex Protocol to Send and Receive Messages
Publication 1770Ć6.5.16 - October 1996
Message Transfer with Message Source Full on the Reply
In this transfer:
•
the message is successfully transmitted on the network
•
the receiver sends a reply but the message source is full,
so the transmitter sends back a DLE NAK
•
the receiver retransmits and the source is no longer full,
so the transmitter returns a DLE ACK
xxxx
Full
OK
OK
xxxx
xxxx
DLE STX xxxx DLE ETX BCC/CRC
DLE STX xxxx DLE ETX BCC/CRC
DLE ACK
Source Transmitter Link Receiver Sink
command
reply
(sometime later ...)
DLE ACK
not full
DLE NAK
DLE STX xxxx DLE ETX BCC/CRC
not full