10 TROUBLESHOOTING

10.3.8 Troubleshooting when communication error "PRO." generates

MELSEC-Q

Symptom

Cause

 

 

Corrective action

MC

 

• Communications were

• Check the Q series C24 communication

 

 

performed with a control

protocol setting and the message from the

 

 

procedure different from

 

 

external device and match the settings, or

 

 

the Q series C24

 

 

correct the message and restart data

 

 

communication protocol

 

 

communications.

 

 

setting.

 

 

• Some of the data are

 

 

 

 

 

different from the control

 

 

 

 

 

procedure.

 

 

 

 

 

• Designated command

 

 

 

 

 

does not exist.

 

 

 

 

 

• The device No.

 

 

 

 

 

designation is not the

 

 

 

 

 

character count

 

 

 

 

 

corresponding to the

 

 

 

 

 

command.

• Check and correct the external device message

 

 

• The characters in the

 

 

message include a data

and restart data communications.

 

 

other than the "A to Z",

Note

Only the data "0 to 9" and "A to F" can be

 

 

"0 to 9", " ", and

•

 

 

control data.

 

handled as character area data during

 

 

 

communications using an MC protocol (ASCII

 

• Communication error

 

 

 

 

 

mode). Therefore, when transmitting a

 

signal "PRO" turned on.

 

 

 

 

 

character string as data, convert the ASCII code

 

 

 

 

of each character string to 2-byte binary code.

 

 

 

Examples)

 

 

 

•

Transmitting the character "G"

 

 

 

 

The ASCII code for the character "G" is 47H

 

 

 

 

and is transmitted as the two bytes 34 H, 37H.

 

 

 

•

Transmitting the character "A"

 

 

 

 

The ASCII code for "A" is 41H and is

 

 

 

 

transmitted as the two bytes 34H, 31H.

 

 

 

 

If the ASCII code 41H for the character "A" is

 

 

 

 

transmitted unchanged, the Q series C24

 

 

 

 

ASCII-BIN conversion will convert it to AH

 

 

 

 

(10) and pass it to the PLC CPU.

 

 

• A device No. outside the

• When designating a device, check "Device

 

 

designated range was

setting" of the parameters written to the CPU

 

 

designated.

and correct it to a device No. within the

 

 

 

designated range and restart data

 

 

 

communications.

 

 

• A remote RUN/STOP

• Check if remote STOP is applied from another

 

 

request was issued

module and restart data communications.

 

 

while remote STOP was

 

 

 

 

 

 

 

applied from another

 

 

 

 

 

module.

 

 

 

 

Bidirectional Non procedure

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