Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 223)

Detailed Flowcharts
Appendix D
DĆ19
Figure D.24
Receiver Routine for FullĆDuplex Protocol
RCVE
Reset Buffer Flag: Set
Header to Illegal Value
GET BUFFER
Get a Buffer
LAST = NAK
Reset Receiver Error Flag
GET CODE
Get Next Input
Control
Code
?
DLE ENQ
?
DLE STX
?
XMSG
Transfer Message to
Network Layer
Ignore
Flag (0)
?
Save Response (ACK or
NAK) in LAST
SEND CTL
Transmit
LAST
No
Yes
No
Yes
No
Yes
Yes
No
NOTE: XMSG Returns ACK,
NAK, 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
11654