Rockwell Automation 1770-KF2 Data Highway or Highway Plus Interface Module User Manual - Manual (Page 174)

Error Reporting
Chapter 7
7Ć19
The meaning of a particular remote error code will vary, depending on the
type of communication interface module at the remote station. For
example, if the remote station is a PLC-3 processor with a 1775-KA
interface module, the remote error codes will have the meanings listed
above. For the meanings of other remote error codes, refer to “ERROR
WORD in User Programming (1771-KG, 1771-KA, 1771-KA2, 1774-KA
Modules),” Errors 80-89.
These counters can be read only by issuing a diagnostic read command
from a device connected to one of the modules that support an
asynchronous port. Therefore, they are available only to a device that can
format the diagnostic commands. A PC user program is unable to initiate
a diagnostic command. The counters occupy a block of the module’s
internal scratch RAM. Most are single byte counters that wrap around to
zero when they overflow. They are used to record events of interest for
debugging and for longer term reliability analysis.
These counters provide a useful tool for diagnosing problems. If a
troubleshooter has available a device that will read the internal error
counters of a module, the ACK timeout counter and the false poll counter
will be useful for diagnosing bad cabling or a noisy or loaded highway
installation. Also useful is the ratio of messages transmitted (successfully
returned an ACK from the remote station) versus the commands sent (but
not necessarily completed).
Important: Because of differences in revision levels in a given module,
and variations from module to module, you must first request the location
of these counters by transmitting to the module a diagnostic status
command. Then, based on the address returned, the number of the
following counters can be used as an offset to calculate the location of the
desired counter, or to calculate how many counter values he wants
returned. This information is then used to format a diagnostic read
command, and the reply from that command will contain the data stored
in the counters.
With the PLC-5, you format the diagnostic read command with a dummy
value for the address. The reply contains the entire counter block.
The counters are divided into two categories:
Data Highway or PCL
Asynchronous
Internal Error Counters