Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 64)

4–10 Using Full-duplex Protocol to Send and Receive Messages
Publication 1770Ć6.5.16 - October 1996
These transfer diagrams show events that occur on various
interfaces. Time is represented as increasing from the top of the
diagram to the bottom. Link-layer data bytes are represented by
“xxxx” and corrupted data by “???”.
For this diagram See page
normal message transfer 4-10
message transfer with NAK 4-11
message transfer with timeout & ENQ 4-12
message transfer with reĆtransmission 4-13
message transfer with message sink full 4-14
message transfer with NAK on reply 4-15
message transfer with timeout and ENQ for the reply 4-16
message transfer with message source full on the reply 4-17
Normal Message Transfer
In this transfer:
•
t he transmitter sends the data to the receiver
•
the sink sends a “not full” message
•
the receiver sends the data to the sink and sends a DLE ACK to
the transmitter
•
the transmitter tells the source that the data was delivered
•
reply is successfully returned
xxxx
not full
OK
OK
xxxx
not full
xxxx
DLE STX xxxx DLE ETX BCC/CRC
DLE ACK
DLE STX xxxx DLE ETX BCC/CRC
DLE ACK
Source Transmitter Link Receiver Sink
command
reply
(sometime later ...)
FullĆduplex Protocol
Diagrams