Mitsubishi Electric MELSEC iQ-R Series User Manual page 445

■C/N
C/N indicates 'Access status with the CPU module'.
Value Status
0001(ON) Error occurred
0000(OFF) Normal
■NAK
NAK indicates "Abnormal completion status".
Value Status
0001(ON) Abnormal completion transmission
0000(OFF) Normal completion transmission or before
data communication
■ACK.
ACK. indicates "Normal completion status".
Value Status
0001(ON) Normal completion transmission
0000(OFF) Abnormal completion transmission or
before data communication
■NEU.
NEU. indicates "Command message to be received/command message in processing".
NEU. is valid only when MC protocol (format 1 to 5) is set as the communication protocol.
This is in the OFF-status when the communication protocol is set to other than MC protocol.
Value Status
0001(ON) Neutral
0000(OFF) Command reception
Description
• The target device issued a data write request to the CPU module when online change is set
to 'Disable' in the parameter settings with Engineering tool.
For functions that cannot be used when online change is set to 'Disable', refer to the
explanation section in each command list in the following manual.
( MELSEC Communication Protocol Reference Manual)
• An error occurred during the access between C24 and the CPU module.
Keeps the ON-status even after the communication returns to normal. Initialize the error
information as necessary.
Page 473 Error Code List

Description
C24 that could not receive data normally sent a response message (NAK message) to the
target device to notice the abnormal completion.
• C24 that could receive data normally sent a response message (ACK message) to the
target device to notice the normal completion.
• Before data is communicated.
Description
C24 that could receive data normally sent a response message (ACK message) to the target
device to notice the normal completion.
• C24 that could not receive data normally sent a response message (NAK message) to the
target device to notice the abnormal completion.
• Before data is communicated.
Description
Waiting for command message to be received.
Command message is in process.
27 TROUBLESHOOTING
27.1 Checking Module Status
27
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