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MELSEC-Q
APPENDICES
Appendix 2 Link Special Relay (SB)
The link special relay (SB) turns on/off by various factors that occur during data linking.
Thus, by monitoring or using it in the sequence program, the abnormal status of the
data link can be checked.
Moreover, the link special relays (SB) that stores the link status are used for the
detailed information of the network diagnostics of GX Developer.
For a list of the device numbers for each display item, see Section 8.1 "Network
Diagnostics (Network Monitor)" and Section 8.3.1 "How to check error codes"
(1) When multiple network modules are mounted
Data in the link special relay (SB) of each network module are refreshed to the
following link special relay (SB) areas of the CPU module when the refresh
parameters of each network module are set to their default.
Module mounting position Module 1 Module 2 Module 3 Module 4
Device number SB0000 to 01FF SB0200 to 03FF SB0400 to 05FF SB0600 to 07FF
(2) Range turned ON/OFF by user and range turned ON/OFF by
system
The link special relay (SB) has the user setting area range (SB0000 to SB001F)
and the system setting area range (SB0020 to SB01FF). (The device numbers
are the example when the network module is mounted in the position of Module
1.)