Undecodable Data Are Transmitted Or Received - Mitsubishi Electric MELSEC iQ-R Series User Manual

When a normal completion response message cannot be received
The following explains how to take corrective actions when a normal completion response message cannot be received upon
command message transmission.
■An abnormal completion response message is received
When a target device received an abnormal completion response message in response to the sent command message, take
corrective action according to the error code in the response message. (Page 473 Error Code List)
When the following problem occurs at the time of access to other station CPU module, clear the programmable controller
CPU information and retry. (Page 455 How to Clear Programmable Controller CPU Information)
• Accessible device range became narrow. (Error code: 7140H)
• Some of commands and/or devices cannot be used (Error code: 7142H, 714DH) etc.
■Response messages cannot be received
Change the setting value for the response monitoring time (timer 1, 5 seconds by default). (Page 422 PARAMETER
SETTING)
If response messages still cannot be received even after changing the setting value, check the communication protocol
setting for the relevant interface, the ON status of the indicator LED, and the connection cable.
■The first part of a response message cannot be received
Increase the setting value of the transmission wait time (the default value is 0 ms). (Page 422 PARAMETER SETTING)
If response messages still cannot be received even after increasing the setting value, reducing the processing time from the
end of transmission processing to the start of reception processing on the target device side is required.

Undecodable data are transmitted or received

Symptom
Data that cannot be decoded
was transmitted and
received.
27 TROUBLESHOOTING
470
27.3 Troubleshooting by Symptom
Cause Corrective action
During multidrop connection,
two or more devices
transmitted data at the same
time.
The parity bit settings do not
match. ■Remarks
If '7 bits' is set to the data bit with the parity bit set to 'Yes' at
The bit length settings for the
one side and '8 bits' is set to the data bit with the parity bit set
stop bit do not match.
to 'None' at the other side, the transmitted/received bit number
will be the same. Therefore, data transmission/reception can
be possible without error.
Transmission speed settings
do not match.
During multidrop connection,
the terminating resistor is not
connected correctly.
When CH1 and CH2 are set
for the interlink operation,
there is an interface to which
the cable is not connected.
■Remarks
If the cable is not connected to one of the interfaces when CH1
and CH2 are used for the interlink operation, the data may be
destroyed due to noise and may result in 'data cannot be
decoded' or 'cause of communications error'.
• Connect the target devices to C24 on a 1:1 basis and
perform a loopback test.
If C24 can communicate normally with each of all target
devices, two or more devices transmit data simultaneously
during multidrop communication. Therefore, interlock the
devices not to transmit at the same time.
• Match the settings of C24 with that of the target device.
• Match the transmission speed of C24 with that of the target
device.
• Connect the terminating resisters to the stations of both
ends. (110  or 330  for C24)
• When using CH1 and CH2 for the interlink operation,
connect the cable to both of the interfaces.
• When using CH1 and CH2 for the independent operation,
reconfigure the setting to the independent operation if it is
set to the interlink operation.
MC Non Bi Pd
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