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MELSEC-Q
6 PROGRAMMING
(5) Checking the forward/reverse loop in the optical loop system
The forward/reverse loop in the optical loop system can be checked not only in
the network diagnostics of GX Developer but also with link special relays (SB)
and link special registers (SW). (Refer to Sections 8.1.1 and 8.1.2.)
(a) Checking the forward/reverse loop of another station
1) When an error occurs on the forward or reverse loop, the following link
special relay (SB) is turned ON.
• Forward loop status (SB0091)
•
Forward loop status of remote master station (SB0092) (Except the
remote master station)
• Reverse
loop status (SB0095)
• Reverse loop status of remote master station (SB0096) (Except the
remote master station)
2) The station where an error occurred can be identified with the following
link special registers (SW).
• Forward loop status of each station (SW0091 to SW0094)
• Reverse loop status of each station (SW0095 to SW0098)
3) If loop switching occurs, the cause of the loop switching is stored in
Loop switch data (SW00D0 to SW00DF).
The position of the loop switch data storage can be checked with Loop
switch data pointer (SW00CF).
4) Cable disconnection or station failure causes loopback.
When loopback occurs, any of the following link special relays (SB) is
turned ON.
• Forward loop loopback (SB0099)
• Reverse loop loopback (SB009A)
5) The station where loopback occurred can be identified with the
following link special registers (SW).
• Loopback station (forward loop side) (SW0099)
• Loopback station (reverse loop side) (SW009A)
6) An incorrect optical fiber cable connection (IN-IN, OUT-OUT) can be
checked with Loop usage status of each station (SW009C to
SW009F).
7) The count of loop switching can be checked with Number of loop
switches (SW00CE).
8) Turning ON Clear loop switch count (SB0009) can clear SW00CE to
SW00DF.
No. Description No. Description
SB0009 Clear loop switch count —
SB0091 Forward loop status
SW0091 to SW0094 Forward loop status of each station
SB0092 Forward loop status of remote master station
SB0095 Reverse loop status
SW0095 to SW0098 Reverse loop status of each station
SB0096 Reverse loop status of remote master station
SB0099 Forward loop loopback SW0099 Loopback station forward loop side)
SB009A Reverse loop loopback SW009A Loopback station (reverse loop side)
—
SW009C to SW009F Loop usage status of each station
SW00CE Number of loop switches
SW00CF Loop switch data pointer
SW00D0 to
SW00DF
Loop switch data