10 TROUBLESHOOTING

MELSEC-Q

(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.

10 - 5

10 - 5