Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual User Manual
Page 175
Error Reporting
Chapter 7
7Ć20
They apply to activity on their respective links. Obviously, the 1771-KA
will have only Data Highway counters. Most modules (including the
KF2) will have both. A KF2 can operate on either the Data Highway or
the PCL; it has a block of counters for each network.
1771ĆKA, 1771ĆKA2, and 1774ĆKA Data Highway Counters
0.
CRC error 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 receiver or transmitter
circuitry on a module is marginal or 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. If 93 is a common error on a
highway system, then expect 37 (start bit timeout) errors also since
any reply that experiences contention will not be retried.
3.
Bad ACK Status: Counts the number of times the ACK was
successfully received but contained a non-zero status code other than
memory full. Currently the only other implemented ACK code is
buffer overflow. This condition should never occur except when
debugging new code.
4.
Returned Messages: Counts the number of times the highway
driver returns a message to sender. Each count corresponds to one
local error bit set or one reply message lost.
5.
Transmit/Memory Full: Counts the number of times that the
receiving station’s memory was full. Each time this happens the
message is placed on a waiting queue for a half second. Each
message will be retried five times for memory overflow before it is
returned to sender.
6.
Poll Timeout: Counts the number of times that this station grabbed
mastership of the highway because it timed out while waiting to hear
a valid frame. On a highway that has just been powered up there
should be only one station that has this counter incremented.