Rockwell Automation Allen-Bradley SynchLink 1756-DM Series Design Manual page 54

4-16
Star Topology Followed by Daisy Chain Topology
Master Node
Hub
Center Node
SynchLink
Publication 1756-TD008A-EN-P - August 2002
Star/Daisy Chain Combination
When using this specialty configuration, you can transition from a star
to a daisy chain configuration or from a daisy chain to a star
configuration. The rules of star and daisy chain configurations apply
to the individual portions. For more information on each, see page 2-2
(Star Topology) and page 2-3 (Daisy Chain Topology).
Figure 4.11
ControlNet
Center Node End Node
43098
Table 4.12 lists more information about this configuration.
Table 4.12
Category:
Time synchronization
Data transfer
Restrictions
Typical applications
(1)
The local ControlLogix controller must move the axis or buffered data for a 1756-SYNCH module. For the
1756-DMxxx module or PowerFlex 700S drives, the device's VPL microprocessor must move the data. For more
information, see page 1-7.
Daisy Chain Topology Followed by Star Topology
Master Node
SynchLink
ControlNet
Explanation:
Master - 1756-SYNCH module
Slaves - Multiple devices, depending on your application
The SynchLink node clock is synchronized across all nodes. Depending
on what other devices are included, you may achieve synchronization
of CST clocks and VPLs as well.
Star portion only
Direct and buffered data can both be used in this configuration.
However, direct data does not offer any benefit to the user because
there is no data pass through in a star configuration as in a daisy chain
configuration.
Daisy chain portion only
To transfer axis or buffered data between nodes, the local controller at
each node must pass the data.
· You cannot transfer axis data with PowerFlex 700s drives or
1756-DMxxx series modules.
· Only one transition between topology types (i.e. you cannot
start with a star, transfer to a daisy chain and then transfer
back to a star)
· You cannot use the daisy chain portion in motion applications.
Center Node
Hub
End Node End Node
(1)
Center
Node
43099