Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 181)

Error Reporting
Chapter 7
7Ć26
19. Received Messages: A 16-bit counter that records the number of
messages successfully received.
20. Not used.
21. Number of ACKs received.
22. Not used.
23. Number of ACKs sent.
24. Not used.
25. Number of NAKs received.
26. Not used.
27. Number of NAKs sent.
28. Not used.
29. Undeliverable Replies: Counts the number of replies that were lost
because they could not be delivered over the highway. Undeliverable
commands can be signaled to the user, because the “user” is located
in PC memory and can always be reached. If a reply message cannot
be delivered over the highway, there is no way to signal the user (of
that message), who is also over the highway, that this station cannot
signal a reply. The local user is not concerned with the problems of
the remote user, and can take no meaningful action anyway, so there
is not much to do but destroy the message and count it.
30. Timeout Preset
31. NAK Preset: Values set by diagnostic commands or set by default
on power-up.
32. ENQ Preset
1771ĆKE/KF, 1770ĆKF2 (Data Highway Mode) Error Counters
DATA HIGHWAY COUNTERS