Mitsubishi-electric QJ71C24N Manuel d'utilisateur télécharger pdf (Page 289)

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MELSEC-Q

10 TROUBLESHOOTING

10.3.11 Troubleshooting when communications is intermittently established and lost

Symptom Cause Corrective action MC

Bidirectional

Non

procedure

• With a multidrop link, two or

more devices transmitted

data at the same time.

• Connect the external devices and the Q series C24 in a

1:1 configuration and perform a communications test.

Since data is transmitted simultaneously from two or

more devices with a multidrop link when normal

communications among all the devices is possible,

interlock the external devices so that they do not

transmit simultaneously.

• The signal cable wiring

connection is faulty.

• Replace the cable, or make the connections firm.

• When "Check CD terminal"

is set, the CD signal is

turned on/off repeatedly.

• Change the wiring so that the CD signal remains ON all

the time, or change the setting to "Do not check CD

terminal".

• When half-duplex

communications is selected,

the ON/OFF timing of each

signal is not matched.

• Control the external device so that the ON/OFF timing

of each signal is matched.

See Chapter 8 of User's Manual (Application).

• Communications are

intermittently established

and lost.

(

• Requested processing of the

next transmission before the

processing of the current

transmission is completed.

• Requested processing of the

next reception before the

processing of the current

reception is completed.

• Make sure to obtain handshake in the sequence

program.

1 The following explains how to take corrective actions when a normal exit response

message cannot be received upon sending of a command message.

1) When a response message of abnormal end is received

When an external device sent a command message and received an

abnormal end response message, take corrective action with the error

according to the error code in the response message (see Section 10.2).

2) When response messages cannot be received

Change the setting value for the response monitoring time (timer 1, default

value is 5 seconds).

(See Section 6.2 of the User's Manual (Application).)

If response messages still cannot be received after changing the setting value,

check the communication protocol setting of the corresponding interface, the

ON status of the displayed LED, and the connection cable.

3) When the first part of a response message cannot be received

Increase the setting value of the message wait time (the default value is 0 ms).

(See Section 6.4 of the User's Manual (Application).)

If response messages still cannot be received after increasing the setting value,

it is necessary to reduce the processing time from the end of transmission

processing to the start of reception processing on the external device side.

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Mitsubishi-electric QJ71C24N Manuel d'utilisateur Page 289

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