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5.5 Self-diagnostic Test
5.5.3 Forward loop test/reverse loop test
5
PREPARATORY PROCEDURES BEFORE
OPERATION
5.5.3 Forward loop test/reverse loop test
The forward loop test/reverse loop test checks a forward or reverse loop side line of the
MELSECNET after connecting all stations via a cable. (Not provided for the
MELSECNET/B data link system)
• Forward loop test
The line is judged by whether the data sent from a forward loop send side of the
master station can be received by a forward loop receive side of the master
station.
• Reverse loop test
The line is judged by whether the data sent from a reverse loop send side of the
master station can be received by a reverse loop receive side of the master
station.
POINT
(1) Execute a forward or reverse loop line test, setting a Q series local station to
the RUN status (Y10=ON).
If the test is conducted in STOP status (Y10=OFF), the master station treats
the Q series local station as a faulty station (relevant bit in D9228 to D9231 is
turned ON).However, the test is normally conducted.
(2) Set link parameters for the master station when executing a forward or
reverse loop back test.(At least set the total number of slave stations)
(1) System configuration
(a) MELSECNET(A1SJ71AP23Q)
An optical fiber cable connects the OUT and IN of all stations.
Figure 5.24 MELSECNET(A1SJ71AP23Q)
Master station
Station
No.02
Station
No.01
Station
No.00
OUT IN
Local station
No.1
Local station
No.2
OUT INOUT IN
Front Front Front
Data flow of forward loop
Data flow of reverse loop
Optical fiber
cable
GX Develope
r