Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 178)

Error Reporting
Chapter 7
7Ć23
25. Replies Received: A 16-bit counter that records the number of reply
messages that were received that resulted in the setting of a done bit
or a remote error bit.
26. Not used.
27. Breaks: Counts the number of breaks sent to the IT.
28. Resynchs: Counts the number of times the PC driver has to
resynchronize with the PC. This counter will always count at least
one resynch (because of power-up).
29. IT Errors: Counts down modulo 5 the number of errors on the
KA-to-IT cable. Every time this count reaches zero the KA does a
handshake to reset the forced I/O table in the PC.
30. 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.
1771ĆKC and 1771ĆKD Error Counters
NOTE: The intelligent device can read the memory of the 1771-KC it is
hooked to by setting the destination equal to the module address.
0. Bad CRC on ACK.
1. ACK Timeout: Counts the number of times that the sender timed
out waiting for an acknowledgment. This is a common error and will
be one of the first to respond to reflections or low level noise on the
highway. It seems to be especially sensitive to problems on longer
cables. It will also show up often if the cable connections are loose.
2. Contention: Counts the number of times contention was detected.
This will also appear quickly on noisy or overlength cables. This
counter corresponds to Error 93.