Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 68)

4–14 Using Full-duplex Protocol to Send and Receive Messages
Publication 1770Ć6.5.16 - October 1996
Message Transfer with Message Sink Full
In this transfer:
•
the transmitter sends a message but the message sink is full,
so the receiver sends back a DLE NAK
•
the transmitter retransmits and the sink is no longer full,
so the receiver returns a DLE ACK
•
a reply is successfully returned
xxxx
not full
OK
OK
xxxx
Full
xxxx
DLE STX xxxx DLE ETX BCC/CRC
DLE NAK
DLE STX xxxx DLE ETX BCC/CRC
DLE ACK
Source Transmitter Link Receiver Sink
command
reply
(sometime later ...)
DLE ACK
DLE STX xxxx DLE ETX BCC/CRC
DLE NAK
DLE STX xxxx DLE ETX BCC/CRC
not full
Full