Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 66)

4–12 Using Full-duplex Protocol to Send and Receive Messages
Publication 1770Ć6.5.16 - October 1996
Message Transfer with Timeout and ENQ
In this transfer:
•
the receiver receives a transmission, but sends back a
DLE ACK that is corrupted
•
the transmitter times out waiting for the DLE ACK and sends a
DLE ENQ
•
the receiver sends back a DLE ACK
•
a reply is successfully returned
xxxx
not full
OK
OK
xxxx
not full
xxxx
DLE STX xxxx DLE ETX BCC/CRC
DL???CK
DLE STX xxxx DLE ETX BCC/CRC
DLE ACK
Source Transmitter Link Receiver Sink
command
reply
(sometime later ...)
DLE ACK
DLE ENQ
(timeout)