Read Request Signal Does Not Turn On Even Though The Target Device Transmitted A Message And The Rd Led Flashes - Mitsubishi Electric MELSEC iQ-R Series User Manual

Read request signal does not turn ON even though the target
device transmitted a message and the RD LED flashes
Symptom Cause
CH Reception data read Communication protocol
request' (X3/XA) does not setting is incorrect.
turn ON even though the
target device transmitted a
message and the RD LED
flashes.
The CD terminal has been
turned OFF when the CD
terminal check is enabled.
When DC control is selected,
the necessary DC codes are
not transmitted.
The end code has not been
received, or the fixed length
data has not been received.
The C24 setting and message
format do not match.
The C24 data
communications monitoring
time is set to "Unlimited wait",
or the monitoring time is too
long.
Corrective action
• Review the communication protocol setting.
• Review the program whether unintended mode switching is
performed when the buffer memory mode switching area is
used for mode switching.
■Remarks
The communication protocol setting contents and the
communication protocol currently in operation can be checked
at the following addresses.
• 'Communication protocol status (parameter setting)'
(Un\G592/608) set by the parameter
• 'Communication protocol status (current)' (Un\G594/610)
currently in operation
• Change the wiring so that the CD terminal remains ON all
the time since a message is skipped if the CD terminal is
OFF when the CD terminal check is set to be enabled.
Check the data transmitted from the target device with the
Circuit Trace function of Engineering tool, and take the
following corrective actions.
• During DC1/DC3 control, if the target device transmits
'DC3(13H)' and interrupts the transmission processing of
C24, transmit 'DC1(11H) at first and then the next message
after the transmission processing of C24 resumed.
• During DC2/DC4 control, if the target device transmits the
next message without adding 'DC2(12H)' after transmitting
'DC4(14H)', transmit a message with 'DC2(12H) added.
Check the data transmitted from the target device with the
Circuit Trace function of Engineering tool, and take the
following corrective actions.
• Match the end code set by the receive end code designation
of C24 with the one sent from the target device.
• Match the data quantity set by the receive end data quantity
of C24 with the data length sent from the target device.
• For communication with the user frame, send the message
with the final frame added to the end from the target device.
■Remarks
When proper data are being transmitted from the target
device, take the corrective action by referring to the
troubleshooting below.
• Page 466 Hardware information communication error
"SIO" occurs
• Page 463 ERR LED flashes
The interpretation of data count, or message format, etc.
varies depending on the settings below. Review the settings of
each item and the operation by the settings in accordance with
the relevant descriptions.
• ASCII-BIN conversion enable/disable
• Transparent code setting
• User frame setting
• Set or shorten the monitoring time and retransmit the
message from the target device and determine the trouble
from the contents of the time-out error.
■Remarks
In the cases below, errors can be detected by setting each
monitoring time (timer 0 to 2).
• When part of a message is skipped.
• When transmission from the target device is interrupted.
For details of the monitoring time, refer to the following
manual.
Page 227 CHANGING DATA COMMUNICATION
MONITORING TIME
MC Non Bi
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27 TROUBLESHOOTING
27.3 Troubleshooting by Symptom
Pd
27
461