Specifications

App - 6
Appendix 3 Link Special Relay (SB) List
The link special relay 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 relay (SB) that stores the link status is used for the detailed
information of the network diagnostics of GX Developer.
When multiple network modules are installed, the SB of each network module is
refreshed to the corresponding SB of the CPU module if each network module’s refresh
parameters are not set. If the refresh parameters are set for at least one network module,
the refresh parameters of all the network modules should be reviewed.
Module installing position Module 1 Module 2 Module 3 Module 4
Device No. SB0000 to 01FF SB0200 to 3FF SB0400 to 05FF SB0600 to 07FF
In the link special relay, there are ranges that the user can set on and off (SB0000 to
SB001F) and that the system can set on and off (SB0020 to SB01FF). (This is the case
in which the unit mounting position is unit 1.)
Link special relay (SB) list
Use permitted/prohibited
Control
station
Normal
station
Remote
master
station
Remote
I/O
station
No. Name Description
Optical Coaxial Optical Coaxial Optical Coaxial Optical Coaxial
SB0000
(0)
Link startup (host) *
1
Restarts the host's cyclic transmission.
Off: Start not instructed
On: Start instructed (valid at rise) *
2
SB0001
(1)
Link stop (host) *
1
Stops the host's cyclic transmission.
Off: Stop not instructed
On: Stop instructed (valid at rise) *
2
SB0002
(2)
System link startup *
1
Restarts the cyclic transmission according to the contents of SW000 to SW004.
Off: Start not instructed
On: Start instructed (valid at rise) *
2
SB0003
(3)
System link stop *
1
Stops the cyclic transmission according to the contents of SW000 to SW004.
Off: Stop not instructed
On: Stop instructed (valid at rise) *
2
SB0005
(5)
Clear retry count
Clears the retry count (SW0C8 to SW0C9) to 0.
Off: Clear not instructed
On: Clear instructed (valid when on) *
2
SB0006
(6)
Clear communication
error count *
1
Clears the communication error (SW0B8 to SW0C7) to 0.
Off: Clear not instructed
On: Clear instructed (valid when on) *
2
[Availability column] Optical: optical loop, Coaxial: coaxial bus
: Available, : Not available
*1: Used in the network tests of GX Developer.
*2: SB0000 to SB0003 become valid when only one point turns on.
SB000 becomes valid.
SB0001 becomes valid.
SB0001
SB0000