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APPENDICES
Appendix 1 List of Special Relays (for Link)
App - 1
APPENDICESINDEX
APPENDICES
Appendix 1 List of Special Relays (for Link)
A special relay (for link) turns ON/OFF due to various causes that are generated during
data link.
Special relays (for link) are used in the sequence program, and data link error status can
be checked by monitoring them.
The following table lists the special relays (for link) available for Q series local stations.
For those used in master and A/QnA series local stations, refer to the following manual.
Type MELSECNET, MELSECNET/B Data Link System Reference Manual
Table App.1 List of special relays (for link)
Buffer
memory
address
(Bit No.)
No. Name Description Details
Hexad
ecimal
Decim
al
103H
(b1)
259
(b1)
M9241
*1
Forward loop
line error
OFF: Normal
ON: Error
•Turns ON when any of the following errors occurs on the forward
loop line between the host and preceding stations.
•Cable disconnection
•Error in the forward loop receiving part of the host station link
module
•Error in the forward loop sending part of the preceding station
link module
•Automatically turns OFF when the error status returns to normal.
103H
(b2)
259
(b2)
M9242
*1
Reverse loop
line error
OFF: Normal
ON: Error
•Turns ON when any of the following errors occurs on the reverse
loop line between the host and the next stations.
•Cable disconnection
• Error in the reverse loop receiving part of the host station link
module
•Error in the reverse loop sending part of the next station link
module
•Automatically turns OFF when the error status returns to normal.
103H
(b3)
259
(b3)
M9243
*1
Loopback
execution
OFF: Not in execution
ON: In execution
•Turns ON while the host station is executing loopback.
103H
(b6)
259
(b6)
M9246
Data
unreceived
OFF: Received
ON: Unreceived
•Turns ON when data have not been received from the master
station.
103H
(b7)
259
(b7)
M9247
Data
unreceived
OFF: Received
ON: Unreceived
•Turns ON, in the three-tier system, when a local station has not
received data from the master station on the higher link.(M9247
is ON when M9208 of the master station is ON.)
103H
(b10)
259
(b10)
M9250
Parameter
unreceived
OFF: Received
ON: Unreceived
•Turns ON when link parameters have not been received from
the master station.
•Automatically turns OFF upon normal reception of the link
parameters.
•The master station sends link parameters to each local station
when switching the loop line.
•Valid when the data-linking loop line is online.