Mitsubishi Electric MELSERVO-J4 Instruction Manual page 135

1. TROUBLESHOOTING FOR SERVO AMPLIFIER (DRIVE UNIT)
Description
Modbus-RTU communication
is not established.
RS-422 communication
(Mitsubishi general-purpose
AC servo protocol) is not
established.
Possible cause
The servo amplifier is not set
to Modbus-RTU
communication protocol.
The communication setting is
not set correctly.
The servo amplifier is not
compatible with Modbus-RTU
communication.
A communication cable is
malfunctioning.
The servo amplifier is not set
to RS-422 communication
protocol.
The communication setting is
not set correctly.
A communication cable is
malfunctioning.
Check result
Check if "communication
protocol selection" in [Pr.
PC71] is correctly set.
Check if [Pr. PC70 Modbus-
RTU communication station
number setting] is set
correctly.
Check if "Modbus-RTU
communication baud rate
selection" in [Pr. PC71] is set
correctly.
Check if "Modbus-RTU
communication parity
selection" in [Pr. PF45] is set
correctly.
For MR-J4-_A_-RJ 100 W or
more servo amplifier, check
that the servo amplifier was
manufactured in January
2015 or later.
Check if MR-J4-_A_ servo
amplifier or MR-J4-03A6(-RJ)
servo amplifier is being used.
Check if the communication
cable has any failure such as
damage.
Check if "communication
protocol selection" in [Pr.
PC71] is correctly set.
Check if [Pr. PC20 Station
number setting] is set
correctly.
Check if "RS-422
communication baud rate
selection" in [Pr. PC21] is set
correctly.
Check if the communication
cable has any failure such as
damage.
1 - 128
Action
Select Modbus-RTU protocol. [A]
Check [Pr. PC70 Modbus-
RTU communication station
number setting] and the
station No. specified in a
Query message from the
controller if they are matched
together.
Check "Modbus-RTU
communication baud rate
selection" and the
communication baud rate
setting of the controller if
they are matched together.
Check "Modbus-RTU
communication parity
selection" and the parity
setting of the controller if
they are matched together.
For MR-J4-_A_-RJ 100 W or
more servo amplifier, use the
one manufactured in January
2015 or later.
(MR-J4-_A_ servo amplifier or
MR-J4-03A6(-RJ) servo
amplifier is not compatible
with Modbus-RTU
communication.)
Replace the communication
cable.
Select RS-422/RS-485
communication (Mitsubishi
general-purpose AC servo
protocol).
Check [Pr. PC20 Station
number setting] and the
station No. specified by the
controller if they are matched
together.
Check "RS-422
communication baud rate
selection" and the
communication baud rate
setting of the controller if they
are matched together.
Replace the communication
cable.
Target
[A]