Rockwell Automation 1756-SYNCH ControlLogix SynchLink Module User Manual - Manual (Page 23)

Publication 1756-UM521C-EN-P - July 2004
Time Synchronization in the ControlLogix System 2-3
Multiple Rockwell Automation products can be synchronized with
SynchLink. In addition to the SynchLink module, the PowerFlex 700S
and the 1756-DMxxx series products (both used for drive control) also
use SynchLink to achieve drive to drive synchronization. While all of
these products maintain interoperability, not all SynchLink features are
incorporated into every product that uses SynchLink; the 1756-SYNCH
module, however, uses all of the SynchLink features.
SynchLink Node Clock
The SynchLink node clock is integral to the SynchLink circuit design.
Any product incorporating SynchLink incorporates the SynchLink
node clock as a base-line requirement. The SynchLink node clock has
a 1μS resolution and is synchronized from node to node when the
SynchLink system is configured.
SynchLink uses a Time Master-Slave mechanism to achieve time
synchronization. During system configuration, you configure one
SynchLink node as the Time Master and all other nodes as Time
Slaves. The SynchLink node that is configured as Time Master
becomes the system clock for the entire SynchLink system. As such,
the SynchLink Time Master broadcasts its time reference to the
SynchLink Time Slaves which adjust their node clocks to be in phase
with the master clock.
Because SynchLink is a unidirectional, broadcasting mechanism, the
master is always placed at the beginning of SynchLink systems using
the star or daisy chain configurations.
Figure 2.1
SynchLink
Time Master
SynchLink
Time Slave
SynchLink
Time Slave
SynchLink
Time Slave
SynchLink
Time Slave
Star Configuration Daisy Chain Configuration
S.L.N.C. = SynchLink Node Clock
S.L.N.C. S.L.N.C. S.L.N.C. S.L.N.C.
S.L.N.C.
S.L.N.C. S.L.N.C. S.L.N.C.
SynchLink
Time Slave
SynchLink
Time Slave
SynchLink
Time Master
Hub
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