Rockwell Automation 1756-SYNCH ControlLogix SynchLink Module User Manual - Manual (Page 46)

Publication 1756-UM521C-EN-P - July 2004
3-18 SynchLink Module Features
CST and SynchLink Mastership
The SynchLink module can be configured for multiple mastership and
slave roles in respect to the Coordinated System Time and the
SynchLink. Table 3.7 describes the ways you can configure your 1756-SYNCH
module’s role in CST Mastership.
Table 3.7 Possible SynchLink Configurations
This configuration: Means:
Only the Make SynchLink CST Master box is checked.
• This module relays time from the Chassis CST Master to the
SynchLink.
• The SynchLink node clock on this module is the SynchLink
Time Master.
• The chassis where the module resides is the CST Time
Master on SynchLink. Although the chassis establishes the
CST value for the SynchLink, the module is not CST master
of the chassis. In this case, another module (e.g. controller)
sets the CST value for the local chassis.
Both the Make SynchLink CST Master and Make Chassis CST
Master boxes are checked This module is the System Time Master. It sets the CST for its local
chassis and all devices connected to the SynchLink.
Only the Make Chassis CST Master box is checked. In this case, you MUST configure the module for its dependence on
SynchLink. The module is a Time Slave on the SynchLink and
depends on the SynchLink fiber optic cable for CST mastership. The
1756-SYNCH module then relays the time from the cable to the
chassis in which it resides, acting as the Chassis CST master. The
1756-SYNCH module’s behavior varies in this configuration,
according to your configuration choices as described in the
following rows
Dependence on SynchLink is Required
• The module is a Time Slave on SynchLink.
• The module is the CST Time Master of the local chassis.
• You MUST have selected another module on the fiber optic
cable to be the SynchLink CST Master.
• If communications with the SynchLink CST Master are not
present when the 1756-SYNCH module powers up,
CST-dependent features will not start operating until the
communications to the SynchLink CST Master are restored.
• If communications with the SynchLink CST Master are
broken after operation has begun, the 1756-SYNCH module
stops relaying time to this chassis, and there will be no CST
signal in the chassis.