Mitsubishi Electric MELSEC iQ-RJ71C24-R2 - Page 453

27 TROUBLESHOOTING
27.1 Checking Module Status
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Self-loopback test
The self-loopback test is a test to check the communication between C24 and the CPU module and the operation of the data
transmit/receive function of C24.
Perform the self-loopback test according to the procedure below.
Operating procedure
1. Connecting cable
• Connect cables to two interfaces as follows:
For the RS-232 interface, connect cables within the connector and install it to the interface.
For the RS-422/485 interface, connect cables on the terminal block.
2. Test mode setting (Page 422 PARAMETER SETTING)
• Set the test mode setting to "Self-loopback test".
• Configure all of the transmission settings for the two interfaces according to the transmission specifications.
• Set the CPU module in the STOP state, and write the parameters.
3. Performing the self-loopback test
• By restarting or resetting the CPU module, the test starts automatically in approximately one second. The RUN LED flashes
during the test. (Set the CPU module in the STOP state.)
• C24 performs the following tests in sequence and repeat them (one test cycle takes approximately one second).
C24 ends the test when all test results become abnormal.
4. Checking the results of self-loopback test
• When the result is normal
This test is performed repeatedly. When the ERR LED is OFF, C24 is operating normally.
• When the result is abnormal
The ERR LED turns ON.
Test item Description LED flashes during the test
Checking communication with CPU module Read and check the CPU module model. RUN LED
Checking the transmit/receive function of interface Send and receive data by changing data. SD LED
RD LED
1
2
3
4
5
6
7
8
9
SDA
SDB
RDA
RDB
SG
SLD
FG
CD(DCD)
RD(RXD)
SD(TXD)
ER(DTR)
DR(DSR)
RS(RTS)
CS(CTS)
CI(RI)
SG
RS-232 interface (D-Sub 9P female) RS-422/485 interface
C24
C24
Cable connection
Cable connection
Signal name
Pin No.
Signal name