Scada-Modbus "No-Response" Troubleshooting Flow Chart (3 Of 5) - Sigma 980 Operating And Maintenance Manual

980 SCADA-Modbus "No-Response" Troubleshooting Flow Chart (3 of 5)

Continued from sheet 2.
Does the
address of the Modbus
message correspond to the NO
address assigned
to the 980?
YES
Does the
Master device use
YES
hardware or software
handshaking?
NO
Are the
correct number of
registers being requested
for the data type
returned?
To ensure the integrity of the data being returned, the 980 checks to make sure
the number of registers being requested coincides with the data type being
returned. If there are inconsistencies the meter will ignore the polling message.
For example, Floating point data requires 2 registers per value. Enumerated
YES
and Integer data requires 1 register per value. Long integers require 2 registers
per value. The meter would ignore a request for just one floating point value
if the number of registers requested was only one instead of 2.
Does the
980 communicate
correctly with the NO
InSight software?
YES
Swap the RX and TX lines
on the serial cable
connected to the 980.
Continued on sheet 4.
Change the Modbus device
address of the 980 in the
"Communications Setup"
menu of the 980.
Disable the handshaking in the
Master device and/or jumper
out the handshaking terminals
in the RS-232 cable.
Call our tech support Calculate the correct number
at 800-635-1230
or data types being returned and
Outside the U.S.A. & Canada,
call +1-970-669-3050
Is the 980
YES
responding now?
NO
NO
of registers needed for the
then change the polling
request accordingly.
SCADA-Modbus® System Guidelines
Appendix E
Congratulations!
You have fixed it.
Page 145