Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual User Manual
Page 176
Error Reporting
Chapter 7
7Ć21
7.
False Poll: Counts the number of times that this station has tried to
relinquish mastership and the station that was expected to take over
failed to respond. This happens often on a noisy highway because
the noise is mistaken for a poll response, and the wrong station is
selected as the next master. When this occurs, the old master
resumes polling. It can happen also on a long highway if the poll
response is very attenuated and is not picked up by the carrier detect
circuit. If the new station does respond, but the old master does not
hear it, the old master will record a false poll and continue polling.
The new master will start polling also. This usually leads to the
second station detecting contention and relinquishing.
8.
Receiver Heard Status: Counts the number of times that the
receiver received a status frame instead of a message frame. This
should occur only if a poll timeout is imminent (a master has had
mastership for more than 170 ms) and the station has disabled its
address recognizer to test for any valid traffic.
9.
Frame Too Small: Counts the number of frames that were rejected
because the header was incomplete. This should be counted only
because of undebugged software or in the unlikely event that a bad
frame fooled the CRC checker.
10. Wrong Destination Address: Counts the number of frames that
were rejected because the destination address was incorrect. This
can have the same cause as #8. This counter also detects frames that
have the same source and destination address.
11. Receiver/Memory Full: Counts the number of times that the
receiver sent an ACK without first being able to allocate a receive
buffer. This will result in a memory overflow error when the next
message is received.
12. Bad Frame Status: Counts the number of frames that were rejected
because of a bad CRC. This error is very common on a noisy
highway.
13. Buffer Overflow: Counts the number of times a message was
received that contained more than 250 bytes.
14. Memory Overflow: Counts the number of times a message was
received when there was no buffer space allocated for it. This
usually follows a memory full error.