• Take corrective action corresponding to the contents of the error.

10 TROUBLESHOOTING

10.3.5 Troubleshooting when communication error "NAK" generates

MELSEC-Q

Symptom

•Communication error signal "NAK" turned on.

Cause

Corrective action

MC

Bidirectional Non procedure

 

 

 

•See section that describes the communication error signal ("C/N", "P/S",

"PRO", "SIO") that are turned on simultaneously when the "NAK" signal is turned on.

Note

Since the error code is added to "NAK" and is transmitted from the Q series C24 to the external device when the "NAK" signal is turned on, take the corrective action described in the error code table (see Section 10.2).

Since the error code added when "NAK" is transmitted is stored to the Q series C24 buffer memory shown below, it can also be checked at the Q series C24.

Error code storage buffer memory address

CH1 side

25AH

CH2 side

26AH

10.3.6 Troubleshooting when communication error "C/N" generates

Symptom

Cause

Corrective action

MC

 

• The Q series C24

• Change to a CPU to which the Q series C24

 

 

cannot be installed in

can be installed.

 

 

the CPU.

 

 

 

• PLC No. designated

• Change the PLC No. to local station (FF), or a

 

 

local station (FF), or a

station No. set with the network parameter and

 

 

station other than a

restart data communications.

 

• Communication error

station No. set with the

 

 

signal "C/N" turned on.

network parameters.

 

 

 

• Routing parameters

• Check the routing parameters and set them up

 

 

between CPU with the Q

to the communications destination CPU.

 

 

series C24 loaded and

 

 

 

communications

 

 

 

destination CPU are not

 

 

 

set.

 

 

Bidirectional Non procedure

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