Link Active Scheduler (Las) - rotork Mk3 Technical Manual

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LINK ACTIVE SCHEDULER (LAS)

Foundation devices may be either Basic or Link Master (LM) devices.

Basic units do not have the ability to hold the timing schedule for scanning the nodes and
cannot act as system controllers.

Every network requires at least one LM to control the network communications. An LM that is
in control of the communications is known as a Link Active Scheduler (LAS). There can only
be one LAS on each FF H1 highway.
All Rotork FF CP cards are supplied set to operate as a Basic device but can be configured to be LMs.
When configured as LMs they are capable of assuming network control by switching automatically to
become the LAS when the highway LAS goes offline. This option must be checked during
commissioning and may be configured as enabled or disabled.
Note:
1. There is limit to the number of VCRs that can be supported by an LAS device. It may be the
H1 gateway (LAS) has a larger VCR capacity than the LM (backup LAS). This could lead to
problems if the number of VCRs is too great and the LM assumes the LAS role.
2. There can be more than one LM on a highway, up to a maximum of eight, but only one will
be the LAS device at any one time. The LMs assume control in the order of their ascending
addresses. When initially setting up a system using FF CP cards that are in Link Master mode,
it is essential to connect the actuators to the bus after the configuration utility is started or
after the DCS gateway port is connected. If an actuator in Link Master mode is connected first,
it will automatically become the LAS (Active Scheduler device) and the DCS H1 gateway will be
unable to gain full control of the network.
Fieldbus power supply
(including terminator)
Power
T
supply
Fig 7.1: Link Active Scheduler – one per network plus Link Master (back-up LAS)
H1 Gateway
JB
Link Master - LM
(can become LAS)
Publication PUB089-005-00_0618
Default
LAS
Trunk – (Main highway segment)
Link Active Scheduler (LAS)
Field Junction Box
(including terminator)
T JB
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