Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 157)

Error Reporting
Chapter 7
7Ć2
An error code word specified in the header rung is the primary source of
explanation for programming problems and run-time problems. Error
codes are stored in this word for most events that can be observed by a
Data Highway user.
The display of an error code at a given location does not necessarily mean
a faulted condition exists on the highway. Due to the nature of the polling
algorithm and the built-in retry and recovery procedures, random noise or
contention can easily be ignored if normal procedures are followed. For
example, Error 89 is primarily an indication of heavy use at one node,
rather than a faulted condition. The appearance of a code like Error 89 is
then a user application question and should be dealt with by
understanding the tradeoffs between performance and node utilization.
Obviously prescan errors (1-29) indicate a program problem and should
be fixed immediately; but merely trapping and halting on run-time errors,
without understanding the relationship of the error to loading factors and
node utilization, does not allow efficient operation of the Data Highway.
A troubleshooter should also make full use of the counter (high byte in the
error word) to record frequency of errors. This contributes to any
application solution that requires redistribution of node traffic.
The error code word is four BCD digits wide. The uppermost digit is not
displayed by the Industrial Terminal in the GET instruction in the header
rung, but this is the least valuable part of the error code and can often be
ignored. If necessary, this number can be easily displayed using GET
BYTE and a PUT. The lower two digits are always the error number.
Each number indicates a different condition, which is explained in the
paragraphs below. The meaning of the upper two digits varies depending
on the error number.
There are about 50 different error numbers that can be reduced to two
major groups and four minor groups:
Pre-Scan Errors: These are mostly communication zone syntax
errors. They are numbered 1 to 29. They are detected as the KA
module prescans the communication zone just before it starts scanning
start bits.
No syntax errors are detected in the header rung. If the prescanner does
not recognize the header rung it will decide that it is not a header rung
and will continue scanning until the end of memory or until it finds a
valid header rung.
ERROR WORD in User
Programming (1771ĆKG,
1771ĆKA, 1771ĆKA2, 1774ĆKA
Modules)