Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 211)

Appendix
D
DĆ1
Detailed Flowcharts
The flowcharts in chapter 10 and 11 give a simplified view of an example
of software logic for implementing full–duplex protocol. In this
appendix, we present flowcharts which give a detailed view of an example
of software logic for implementing full–duplex protocol.
We have not shown any error checking or recovery relating to interaction
with the modem handshake driver, a third process. To do this would
overly complicate the flow charts, and in many cases, such error checking
and recovery are not needed.
Figure D.1
Data Flow Program for Full-Duplex Protocol
Data Link Layer
Physical
Link
Layer
SENDCTL
SENDDATA
SENDETX
XMIT
Network
Layer
GETCODE RCVE
Empty
Buffers
Received
Messages
Messages
to be sent
Messages
Which
Have Been Sent
(Or Have Failed)
Row Output
Bytes
Messages
DLE
ENQ
Separa-
tor
Row Input
Bytes
Messages
DLE
ENQ
DLE ACK
DLE ACK
DLE NAK
10071–I
Multiplexer
Overview