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U N I V E R S A L M OTO R C O N T R O L L E R U M C 1 0 0 . 3 | M R P 3 1 . 0 M O D B U S T C P C O M M U N I C AT I O N M O D U L E M A N U A L
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Diagnosis
Diagnosis and behavior in case of an error
The MRP31.0 module provides diagnosis information about the status of the connected UMC100.3, its own status and the
status of the Modbus connection. Diagnosis information is shown
- with the locally available LEDs and
- via Modbus services.
Checklist
In case of trouble use the following checklist to track down the problem:
RS485
• Are the termination resistors placed at the end of the line?
• Never place any termination resistors on a drop cable.
• Is the line polarity correct? Are the lines by accident swapped?
• Is the maximum line length exceeded?
MODBUS parameters
• Is the baud rate correctly adjusted?
• Is the MODBUS master in RTU mode?
• Is the slave address correct?
• Are there two devices with the same address in the system?
MODBUS master
• Is the request to response timeout correct?
• Is the MODBUS silent interval between two telegrams > 3.5 character times?
• Notice that the slave device will not give any response when it is addressed with a broadcast (slave address = 0)
MODBUS slave
• Has the device a unique MODBUS address?
• Same baud rate set as used in the master?
• Is the function code supported?
• Has the request a valid quantity of coils, inputs, registers?
• Power supply turned on?
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