Biddle Modbus Manual page 39

5
. . Errors
5.1 Resolving simple problems
PROBLEM
The unit does not respond to Mod-
bus commands.
The unit functions differently from
expectations.
The values of the readings are not
correct.
There are errors in the communica-
tion.
Manual for software version U3.0 – 01 (22-06-2017)
POSSIBLE CAUSE
No communication with the Mod-
bus network.
The distance between the Modbus
system and the first unit is too
great, which results in the module
not getting enough power supply.
The wiring has been connected
wrongly.
The unit has an incorrect Modbus
node address.
The baud rate of the Modbus sys-
tem has been set wrongly.
The unit is controlled temporarily
via the b-touch control panel.
The wrong register address is being
read out.
The read-out type is incorrect.
Poor Modbus cabling.
Excessively long Modbus cabling.
SOLUTION
• Check the connection and the
cables of the Modbus network.
• Remove excess control cable.
• Reverse the Modbus A- and
Modbus B+ connections.
• Check the unit's Modbus node
address.
• Set the Modbus system to the
correct baud rate.
Default value is 9600.
• Changes via the b-touch control
panel apply only until the starting
time of the next switching
moment by Modbus.
• If desired, modify the associated
register address so that changes
via the b-touch control panel are
not permitted.
• Read out the correct register
address.
• It may occur that the system
uses a value of 1 higher. In that
event, use 101 for register
address 100, for example.
• Check the type of the address.
• Replace the cabling with better-
quality cabling.
• Remove excess cabling.
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