Справочник Пользователя для Mitsubishi Electronics QJ71C24/-R2
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MELSEC-Q
10 TROUBLESHOOTING
10.3.4 Troubleshooting when an external device transmitted a message and "RD" LED
blinked, but the Read Request signal was not turned ON
Symptom
Cause
Corrective action
MC
Bidi
rectio
na
No
n
procedure
• Communication protocol
is set incorrect.
•
Check if the communication protocol is set correctly.
•
Check if the mode was switched without using the
buffer memory mode switching area.
Note
•
The communication protocol setting contents and
the communication protocol in the current operation
can be checked at buffer memory addresses 250
H
to (CH1) and 260
H
(CH2).
• When "Check CD
terminal" was set, the CD
terminal was turned off.
•
Since messages are skipped when the CD terminal is
turned OFF when "Check CD terminal" is set, change
the wiring so that the CD terminal remains on all the
time.
the wiring so that the CD terminal remains on all the
time.
• When DC control is
selected, the necessary
DC codes are not
transmitted.
• Check if a message is transmitted without transmitting
"DC1 (11
H
)" after the external device transmits "DC3
(13
H
)" during DC1/DC3 external control.
• Check if the next message is transmitted without
adding "DC2 (12
H
)" after the external device transmits
"DC4 (14
H
)" during DC2/DC4 external control.
• The end code was not
received, or fixed length
data was not received.
•
Check if the end code set at the Q series C24 and the
end code transmitted from the external device are the
same.
same.
•
Check if the external device transmitted the fixed
length designated at the Q series C24.
•
Check if the trailer frame was transmitted during
communications by user frame.
Note
•
When the send data from the external device is
correct, take the corrective action described in
Sections 10.3.10 and 10.3.11.
Sections 10.3.10 and 10.3.11.
• The Q series C24
setting and message
format do not match.
• The data count basics, message format, etc. depend
on the following settings.
⋅
ASCII-BIN conversion enable/disable
⋅
Transparent code setting
⋅
User frame setting
See the relevant section for a description of operation
according to the set contents and setting of each item.
according to the set contents and setting of each item.
• An external device
transmitted a message
and "RD" blinked, but
the read request signal
(X0) was not turned
ON.
• The Q series C24 data
communications
monitoring time is set to
"infinite", or the
monitoring time is too
long.
•
Set, or shorten, the monitoring time and retransmit the
message from the external device and determine the
trouble from the contents of the time-out error.
trouble from the contents of the time-out error.
Note
•
Error detection by the watchdog timer (timer 0 to
timer 2) is possible in the following cases.
⋅
When part of a message is skipped.
⋅
When transmission from an external device is
interrupted.
See Chapter 6 of User's Manual (Application) for a
detailed description of the monitoring time.
detailed description of the monitoring time.