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8 PROGRAMMING
MELSEC-QnA
8.4 Link Special Relay/Register (SB/SW)
The data link status can be checked with bit data (link special relay SB) and word data
(link special register SW).
The SB and SW are used to conveniently express the information on the buffer
memory of the master and local modules. They are read and written before use with
FROM/TO instructions.
• Link special relay (SB).................. Buffer memory address 5E0
H to 5FFH
• Link special register (SW) ............ Buffer memory address 600
H to 7FFH
8.4.1 Link special relay (SB)
SB0000 to SB002F is turned on/off with the sequence program, and SB0030 to
SB00FF is automatically turned on/off.
Refer to Section 3.5.2 (4) for correspondence with buffer memory.
When using a master/local module as a standby master station, refer to the respective
columns under "Availability" in the table as explained below.
• When a standby master station is operating as a master station: "Master station"
column
• When a standby master station is operating as a standby master station: "Local
station" column
Table 8.1 Link special relay list
Availability
(
: available,
: not available )
Online
Number Name Description
Master
station
Local
station
Offline
SB0000 Data link restart
When parameter data change is not made to the data link which was
stopped by SB0002, restart it with this signal. (If you have changed
parameter data during a data link stop, turn on Yn6 and Yn8 to restart a
data link.)
OFF : No restart specification
ON : Restart specification
SB0001 1
Master station switching
data link start
The output information is switched from the standby master station to
the master station to start the data link (Usable in standby master
station).
OFF : No switch instruction
ON : Switch instruction
SB0002 Data link stop
Stops the host station's data link.
However, when the master station executes this, the entire system
stops.
OFF : No stop specification
ON : Stop specified
SB0004 1
Temporary error invalid
station request
Confirms the station which had been specified by SW0003 to SW0007
to temporary error invalid station.
OFF : No request
ON : Request
SB0005 1
Temporary error invalid
station cancelling request
Cancels the station which had been specified by SW0003 to SW0007
from temporary error invalid station.
OFF : No request
ON : Request
SB0008 1 Line test request
Performs the line test to station which had been specified by SW0008.
OFF : No request
ON : Request
SB0009 1
Parameter setting test
request
Reads the parameter setting information for actual system
configuration.
OFF : Requested
ON : Not requested
1: Link special relay added to the function version B or later