EGW1-IA3-MB-DF1 – Modbus TCP a DF1 User’s Manual
Exemys
www.exemys.com
Rev. 1
24
B. Modbus statistics
You can monitor the internal statistics by reading Modbus locations. These data are the same that those
provided through the web service. Think of this method as a way to gather statistics by means of a
SCADA that eventually could store a log just by issuing periodical Modbus TCP reads. Statistics registers
are made public through Input Status locations, as shown below
Meaning
Input Status
Malformed requests
30001-30002
Discarded requests due to buffer overflow
30003-30004
Table look-up misses
30005-30006
Embedded Slave
Requests discarded
30007-30008
Requests accepted
30009-30010
Gateway
Successful transactions
30011-30012
Timed out
30013-30014
Requests discarded due to serial errors
30015-30016
Errors reported by the PLC
30017-30018
Valid requests
30019-30020
Registers shown above in bold letters represent the totals (i.e. a request is either malformed, discarded
because the TCP buffering feature is disabled or valid). By the other hand, the addition of the remaining
registers compounds the valid requests. We call valid requests to those that can be processed,
disregarding whether they contain solvable or unsolvable requests. For example, if no translation could
be performed because the target was not found in the tables, the request is syntactically valid, though it
cannot be solved (this is known as a table look-up miss).
Note that two Input Status are used to represent each record. This is because the internal representation
of the counters is 32 bits wide. The first Input Status shows the upper 16 bits and the second Input Status
shows the remaining (least significant bits).
To reset the statistics using the Modbus TCP Slave, just write any value to Holding Register 40001.
