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Recognizes and adds new devices to the link.
Removes non-responsive devices from the link
Distributes Data Link and Link Scheduling time on the link. The data link layer
synchronizes the network-wide Data Link Time. Link scheduling time is a link
specific time represented as an offset from Data Link Time. It is used to indicate
when the LAS on each link begins and repeats its schedule. System Management
uses it to synchronize function block execution with the data transfers scheduled by
the LAS.
Polls devices for buffered data at scheduled transmission times.
Distributes a priority-driven token to devices between scheduled transmissions.
Any device on the link may become the LAS as long as it is capable. The devices that are
capable of becoming the LAS are called Link Master devices. All other devices are
referred to as Basic devices.
The FIM is Link Master capable and supports both primary and backup link schedules. It
is designated as the primary Link Master. It is always assigned the lowest network
address.
Upon startup or failure of the existing LAS, the Link Master capable devices on the link
bid to become the LAS. The Link Master that wins the bid begins operating as the LAS
immediately upon completion of the bidding process. The Link Master capable device
with the lowest address usually wins the bid. Link Masters that do not become the LAS
act as basic devices when viewed by the LAS. They also act as LAS backups by
monitoring the link for failure of the LAS, and by bidding to become the LAS when a
LAS failure is detected.
R400
Experion PKS Series A Fieldbus Interface Module User's Guide
July 2010
3. Fieldbus Integration With Experion System
Honeywell
3.4. Link and Block Schedules
65
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