Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 65)

4–11 Using Full-duplex Protocol to Send and Receive Messages
Publication 1770Ć6.5.16 - October 1996
Message Transfer with NAK
In this transfer:
•
the transmitter sends corrupted data to the receiver and the
receiver responds with a DLE NAK
•
the transmitter retransmits and the transmission is successful
•
the receiver sends a DLE ACK to the transmitter
•
reply is successfully returned
xxxx
not full
OK
OK
xxxx
not full
xxxx
DLE STX x???x DLE ETX BCC/CRC
DLE STX xxxx DLE ETX BCC/CRC
DLE NAK
DLE ACK
DLE STX xxxx DLE ETX BCC/CRC
DLE ACK
Source Transmitter Link Receiver Sink
command
reply
(sometime later ...)