Loopback Test - Mitsubishi Melsec-L Series User Manual

6.5 Loopback Test

(Procedure 1) Connecting the C24 to an external device
(Procedure 2) Switch setting with GX Works2
(Procedure 3) Performing a loopback test
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A loopback test performs a communication test using the loopback test function of the
MC protocol, in order to check the connection between the C24 and an external device,
the communication function of each device, and the operation of the communication
program of the external device.
Turn off the power to the station on which the C24 is installed and connect a
communication cable to an external device to perform data communication using the
MC protocol (Refer to Sections 6.2 and 6.3).
(1) Set the switch settings with GX Works2 as shown in Section 7.3 and write the
parameters to the CPU module in order to perform data communication using the
MC protocol.
(2) The following shows an example of the settings when performing a loopback test
on the interface on the CH1 side.
Item
Operation setting
Data Bit
Parity Bit
Transmission Odd/even parity
Setting
Stop bit
Sum check code
Online Change
Setting modifications
Communication rate setting
Communication protocol setting
Station number setting
(1) Set the CPU module to the STOP status, and turn on or reset the CPU module
(communication is enabled for approx. one second).
(2) Create a program for a loopback test on the external device side and send a
command message such as the following to the C24.
The commands used are as follows:
•
When performing communication test in an A compatible 1C frame:
TT command (For an example, refer to the next page)
•
When performing communication test in a QnA compatible frame:
0619 command
When performing communication tests in a QnA compatible frame, refer to the
following.
MELSEC-Q/L MELSEC Communication Protocol Reference Manual
Setting value
Independent
7
Exist
Odd
1
None
Enable
Disable
9600bps
MC protocol (Format 1)
0
6 SETTING AND WIRING
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