Scada-Modbus "No Response" Troubleshooting Flow Chart (2 Of 5) - Sigma 980 Operating And Maintenance Manual

Appendix E

980 SCADA-Modbus "No Response" Troubleshooting Flow Chart (2 of 5)

Continued from sheet 1.
Is the
Master device
configured for 7 data bits,
1 stop bit, even
parity?
YES
Is there a
constant 5–18 VDC
between pins C and B (GND)
of the RS-232 cable
on the 980?
YES
Does the
baud rate of the
980 match that of the Master
device?
YES
Continued on sheet 3.
Page 144
SCADA-Modbus® System Guidelines
Can the
Master device be
NO configured for
7, 1, even?
YES
Configure the Master device
for 7 data bits, 1 stop bit
and even parity.
Configure the Master device
that is communicating with the
980 to keep the DTR (Pin C)
NO
of the flow meter constantly
held high for the duration of all
communications.
Set the baud rate of the 980
NO to match that of the Modbus
Master device.
Obtain a protocol converter
to convert the communication
NO
parameters to 7 data bits,
1 stop bit, and even parity.
This section does not apply
to Modem Communication.