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8 PROGRAMMING
MELSEC-Q
8.4 Link Special Relays and Registers (SB/SW)
The data link status can be checked with bit data (link special relays: SB) and word
data (link special registers: SW).
The SB and SW represent the information in the buffer memory of the master/local
module, which is used by reading to the device specified in an automatic refresh
parameter.
• Link special relays (SB) : Buffer memory addresses 5E0H to 5FFH
• Link special registers (SW): Buffer memory addresses 600H to 7FFH
8.4.1 Link special relays (SB)
Link special relays SB0000 to SB003F are turned ON/OFF by the sequence program,
and SB0040 to SB01FF are automatically turned ON/OFF.
The values in parentheses in the number column indicate the buffer memory address.
When the standby master station is controlling the data link, the availability of the link's
special relays is basically identical to that of the master station.
When the standby master station is operating as a local station, the availability of the
link's special relays is identical to that of a local station.
For the correspondence with the buffer memory, see Section 8.3.2 (5).
Table 8.5 Link special relay list (1/5)
Number
SB0000
(5E0H, b0)
SB0001
(5E0H, b1)
SB0002
(5E0H, b2)
SB0003
(5E0H, b3)
SB0004
(5E0H, b4)
SB0005
(5E0H, b5)
SB0008
(5E0H, b8)
SB0009
(5E0H, b9)
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Name
Description
Availability
: Available, : Not available)
Online
Offline
Master station
Local station
(
Restarts the data link that had been stopped by SB0002.
OFF: Restart not instructed
ON : Restart instructed
Instructs to perform cyclic data refresh after the data link control is
Refresh instruction at
transferred to the standby master station.
standby master
OFF: Not instructed
switching
ON : Instructed
Stops the host data link.
However, when the master station executes this, the entire system
Data link stop
will stop.
OFF: No stop instruction
ON : Stop instructed
Refresh instruction
Instructs to refresh cyclic data after changing parameters by the
when changing
RLPASET instruction.
parameters by the
OFF: Not instructed (stop refreshing)
dedicated instruction
ON : Instructed (start/continue refreshing)
Establishes the stations specified by SW0003 to SW0007 as
Temporary error
temporary error invalid stations.
invalid request
OFF: Not requested
ON : Requested
Cancels the temporary error invalid status of stations specified by
Temporary error
SW0003 to SW0007.
invalid canceling
OFF: Not requested
request
ON : Requested
Executes line tests for the stations specified by SW0008.
Line test request
OFF: Not requested
ON : Requested
Reads the parameter setting information for the actual system
Parameter information configuration.
read request
OFF: Normal
ON : Abnormal
Data link restart
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