Product manual

TAC Xenta Server – Gateway, Technical Manual 12 Working with Third-party Communication Diagnostics
Schneider Electric Buildings AB, June 2011 105 (184)
04-00124-06-en
Example log: Modbus Timeout Error
The messages prefixed by !MBM in this log indicate that a Modbus
device has not responded. The most likely cause of such errors depends
on how many target devices are affected. Consider, therefore, the fol-
lowing:
• If the fault is to a single unit only, then this indicates a fault in that
particular device, or possibly the wiring to it. Alternatively, it may
indicate an address mismatch in the Xenta 913 configuration.
• If all units have failed, this is an indication of a fault in the
Xenta 913 equipment, or possibly the serial connection to it. Alter-
natively, it may indicate the incorrect setting of the Xenta 913
communications parameters.
In any case, it is important to check all cabling and the configuration of
the Xenta 913 and associated slave devices whenever communication
errors occur. The likely importance of errors depends on how regularly
they occur. Consider, therefore, the following:
• Infrequent errors may indicate a noisy cable, but can often be
ignored. However, if the error frequency is such that one or more
devices are falsely flagged as failed, then corrective action is
required.
• If errors such as “checksum mismatch” or “bad data” occur regu-
larly, then this most probably indicates a software bug or protocol
implementation error. Such errors need to be reported to Schneider
Electric for correction, preferably accompanied by a representa-
tive log file.
The following screen capture shows the example values page contain-
ing communication status values for the Modbus Master example. For
a log containing the same number of time-out as the preceding example,
it is quite common for all status values to show FAILED. Of course, if
the interface was working previously, then the FAILED status values
would indicate that a hardware fault had just arisen on the target system.