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 connectthe 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
4-94
I
•
To Next Page
Loading...
