MITSUBISHI ELECTRIC QJ71C24N - Manual (Page 256)

10 - 5 10 - 5
MELSEC-Q
10 TROUBLESHOOTING
(a) When a communication error occurs, take corrective action according to
Section 10.3.
(b) The initial status of the LED ON and communications error indicates the
status when the Q series C24 starts up by turning on the power or resetting
the PLC CPU.
(c) Each of the communications error status, C/N to SIO, CH1 ERR. and CH2
ERR., turns on when an error occurs, and keeps its on-status even after the
communication returns to normal.
The PLC CPU can check the aforementioned LED ON status and
communications error status, and initialize any error information using
read/write to the buffer memory of the Q series C24 and input/output signals.
Initialize the error information according to Section 10.1.2.
(d) NAK to NEU. (No. 6 to 8) turn on/off depending on the status.
(e) SD WAIT turns on when data cannot be sent to the external device by the
transmission control of the Q series C24 (waiting for data transmission).
• When transmission cannot be started.
• When a transmission pause request is received during data transmission.
(DSR signal is off, reception by DC3)
SD WAIT turns off when transmission becomes possible and data
transmission is started/resumed.