10 TROUBLESHOOTING

MELSEC-Q

10.3.2Troubleshooting when "RD" LED does not blink even though an external device is transmitting a message

Symptom

 

Cause

 

 

Corrective action

MC

 

 

 

• Check if the Q series C24 and external RD and

 

 

Signal lines are not

 

SD signal lines are cross connected.

 

 

• Use the external device OPEN statement to

 

 

 

connected correctly.

 

 

 

 

check if the opened port and the cable

 

 

 

 

 

 

 

 

 

 

connection port are matched.

 

 

 

 

• Connect the wiring so that the "DSR", "CS", and

 

• "RD" does not blink

External device

 

other transmission control signals are ready.

 

 

transmission control

 

Note

 

 

even through an

 

 

 

 

 

signals are not turned

 

• Since the control signal specifications depend

 

external device is

 

 

 

 

ON.

 

on the device, connect the wiring by seeing

 

transmitting a message.

 

 

 

 

 

 

the instruction manual of the device used.

 

 

 

 

 

 

 

• If the message passes

 

 

 

 

 

 

through an RS-232

 

 

 

 

 

 

RS-422 converter,

• Check the specifications of the converter and

 

 

 

modem, etc., the signal

 

modem and recheck the settings and wiring

 

 

 

is interrupted at one of

 

 

 

 

 

 

the intervening devices.

 

 

 

 

 

 

 

 

 

 

 

Bidirectional Non procedure

10 - 30

10 - 30