Rockwell Automation 1775-KA PLC-3 Communication Adapter Module User Manual - Manual (Page 213)

Detailed Flowcharts
Appendix D
DĆ3
Figure D.3
Receiver Routine for Full-Duplex Protocol
RCVE
GET BUFFER
Get a Buffer
LAST = NAK
Reset Receiver Error Flag
GET CODE
Get Next Input
DLE STX
?
XMSG
Transfer Message to
Network Layer
Ignore
Flag (0)
?
Save Response (ACK or
NACK) in LAST
SEND CTL
Transmit
LAST
No
Yes
No
Yes
No
Yes
Yes
No
NOTE: XMSG Returns ACK,
NACK, or 0 (for Ignored Message)
Variables:
•
LAST: Value of Last Response
•
HEADER: DST, SRC, CMD, STS
and TNS from last message
•
BUFFER: Whether an Empty Buffer is Read
•
Receiver error flag
10073–I
Reset Buffer Flag; Set
Header to Illegal Value
Control
Code
?
DLE ENQ
?