Mitsubishi MELSEC-A Series Reference Manual page 246

8. PROCEDURES TO OPERATION
(3)
(4)
Test procedure
The following flowchart shows the operation procedure for forward loop test/reverse
loop test.
Test result
The LEDs on the link module of the master station or the GPP link monitor function
show(s) the test result.
(a) For GPP link monitor, refer to Section 10.1.
(b) The descriptions of the LEDs are as follows.
1) Normal.....The following LEDs flash in order:
CRC, OVER, AB.IF, TIME, DATA, UNDER
2) Error........ The corresponding LEDs flash and the test is discontinued.
a) When the TIME, DATA and UNDER LEDs flash:
POINT
In case of forward/reverse loop error, the data link will be established in the
reverse/forward loop or the loopback mode.
The forward/reverse loop data link is recovered when the loop returns to normal.
The LEDs remain in the error status even after the recovery, reset the master
station and execute the forward loop test/reverse loop test again.
Hardware failure
Disconnection of the optical fiber/coaxial cables, or loopback
due to a slave station error
The master station (00) setting is made for more than one
station.
The monitoring time set is too short.
8 - 23