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MELSEC-Q
10 TROUBLESHOOTING
(3) Checking by GX Configurator-SC
Display the "Monitor/test others" screen.
For details on display screens, see Section 8.6.9 of the User's Manual (Basic).
(4) Description of LED ON status and communications error status
Related protocol
No.
Status
signal
name
Description
Description when ON
(when LED is turned on
(1))
Description when OFF
(when LED is turned off
(0))
Initial
state
MC
Non
procedure
protocol
Bidirection-
al protocol
1 SD WAIT Transmission wait status
Waiting for data
transmission
Data transmission start OFF
Overrun or framing
error occurred.
OFF
2 SIO SIO error status
OS area is full.
Received data was
deleted.
Normal
OFF —
3PRO.
Communication protocol
error status
Error occurred. Normal OFF
—
4P/S
Status of parity error or
sum check error
Error occurred. Normal OFF
5C/N
Access status with the
PLC CPU
(
1
)
Normal OFF
6NAK
Abnormal completion
status
Abnormal completion
transmission
Normal completion
transmission
OFF
7ACK.
Normal completion
status
Normal completion
transmission
Abnormal completion
transmission
OFF
8NEU.
Neutral status
Waiting to receive
command
Neutral Command reception
(
2
)
—
9 CH2. ERR
Error occurrence status
on CH2 side
OFF
10 CH1. ERR
Error occurrence status
on CH1 side
Switch setting error
Mode switching error
Transmission error
Reception error
On-demand error
Normal
OFF
1 C/N turns on in the following cases:
• An external device issued a data read request to the PLC CPU when write
during RUN is set to prohibit in the switch settings by GX Developer (see
Section 4.5.2).
For functions that cannot be used when write during RUN is set to prohibit, see
the explanation section in each command list of the Reference Manual.
• When an error has occurred during access between the Q series C24 and the
PLC CPU.
2 NEU. is valid when a target interface is set to use the MC protocol.
When the target interface is set to other than the MC protocol, the status of NEU.
is off.