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4.A2CCPU
- - _ - - - - - - - - - - - - - - - - - MELSEC·A
4.10.4 Self-loopback test
. Self-Ioopback test mode: Mode selection switch set in "7'
In this mode, the link module hardware is tested independently of the link.
Data are sent from the send port in the forward loop and received at the
receive port in the forward loop. Whether the hardware is normal or faulty
is found according to whether the data are received within the predeter-
mined period of time.
The same check is made for the reverse loop.
SR
SR
(1) Test status
• Connect a cable (coaxial cable or fiber-optic cable) from the forward
loop send port to the forward loop receive port in the same module.
Similarly connect the send port to the receive port in the reverse loop.
• For the station to be tested, set the RUN key switch in the STOP
position.
For a remote I/O station, place the master station in the STOP state.
• After placing the mode select switch in "7' and reset the module using
the reset switch.
(2) Test result
Determine the test result by the LEOs provided at the front panel of the
link module.
• Normal:
The following six LEOs flicker sequentially.
CRC. OVER, AB.IF, TIME, DATA, UNDER
• Faulty:
The LEOs which correspond to the detected error lights and the test
is stopped.
Example:
Forward loop cable is broken
The following LEOs light.
F.LOOP, R.LOOP, DATA
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