21
[connection example 1: redundant configuration of switching hubs]
CobraNet PRIMARY
CobraNet SECONDARY
CobraNet PRIMARY
(Operating)
CobraNet
SECONDARY
CobraNet
PRIMARY
CobraNet
SECONDARY
(Operating)
SR-D8-M
CobraNet unit B
CobraNet unit A
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB 6
5
4
3
2
1
As shown in the example above, when the CobraNet unit A is operating via the CobraNet PRIMARY and the
CobraNet unit B is operating via the CobraNet SECONDARY, 6 switching hubs are used for communications
between both units. Therefore, in a redundant configuration of switching hubs*, the number of hubs cascade-
connected from the SR-D8-M should be 3 or less.
* A method of connecting a single unit’s CobraNet PRIMARY and SECONDARY terminals to each different
switching hub to prevent the system from going down when a cable is broken or power fails.
[connection example 2: Non-redundant configuration of switching hubs]
SR-D8-M
CobraNet unit C
CobraNet unit B
CobraNet unit A
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
SW-HUB
1
2
3
4
5
6
7
8
CobraNet PRIMARY, SECONDARY
Star connections
As 7 switching hubs are on the communication path from the CobraNet unit A to the CobraNet unit B, there is
no problem for the system. However, as the number of hubs from the CobraNet unit A to the CobraNet unit C is
8, there may be a system failure.