Scada-Modbus "No Response" Troubleshooting Flow Chart (5 Of 5) - Sigma 980 Operating And Maintenance Manual

980 SCADA-Modbus "No Response" Troubleshooting Flow Chart (5 of 5)

Returned values do not match
the values in the 980 display.
Are you SURE
the correct register
addresses are being requested
for the values you
want returned?
YES
Are you
SURE the Modbus
deviceaddress of the
980 is correct?
YES
Does the baud
rate of the 980 match that
of the Modbus Server?
YES
Are the
integer values for
Units of Measure being
returned correctly?
YES YES
Have you
configured the Modbus
server and/or MMI, to interpret
the Channel Data being
returned as floating
point values.
NO
Configure the Modbus server and/or
MMI to interpret the channel data
being returned as 32-bit floating point
values. If you're not sure how to do
this, conatct the server or MMI
manufacturer for assistance.
e.g., If polling for flow, are you requesting register 40033?
Verify the correct register
addresses in Appendix H and
change the address of the
NO
registers being requested
as needed.
Check the Modbus device
address in the Communications
NO
Setup menu of the 980.
Change as needed.
Change the baud rate in
either the 980 or the Modbus
NO
server so that both are set
to the same baud rate.
Have you
configured the Modbus
server and/or MMI to interpret
NO
the Units of Measure
as integer values?
YES YES YES
Use either a protocol analyzer or a
communications diagnostic program
running on a PC to intercept and
verify the Modbus response message
from the 980.
Configure the Modbus server
and MMI to interpret the values
being returned for Units of
NO Measure as 16-bit integer values.
If you're not sure how to do this,
contact the server or MMI
manufacturer for assistance.
Make a note of the Modbus
message and then call SIGMA
Tech Support to have the
SCADA-Modbus® System Guidelines
Appendix E
Modbus Response
Message validated.
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