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3. Fieldbus Integration With Experion System
3.4. Link and Block Schedules
ATTENTION
If the LAS is too large to fit in the active Link Master capable device, the user
must reconfigure the device to become a Basic one through Control Builder,
and restart the device to initiate the change.
Most Link Master capable devices can only support one subschedule and
cannot support blocks that are running two different macrocycles. Each
macrocycle includes one subschedule. Each subschedule includes
sequences that specify the start time of each element in the sequence. The
elements are actual publications that initiate schedule operations. Devices
have predefined limits on the number of subschedules that can exist per LAS
and the number of sequences that can exist in a subschedule. If the number
of subschedules and/or sequences in the current schedule (backup LAS)
exceed the Link Master capable device's predefined limits, a load of the
device through Control Builder will generate load errors identifying
subschedule problems. In this case, the user must reconfigure the device to
become a Basic one through Control Builder, and restart the device to initiate
the change. Otherwise, if the FIM fails, the potential for a "no schedule"
condition exists. Since the schedule is cleared from the Link Master capable
device upon the detection of load errors, it cannot function as the backup
LAS without a schedule.
Link Schedule
The Link Schedule is the overall schedule for the link. It includes both the link data
transfer and the device function block execution schedules. A Link Schedule is provided
for the FIM interface port for each link. A backup Link Schedule is provided for all Link
Master capable devices on the link.
The link data transfer schedule is derived from the portion of the link schedule that deals
with publication of parameters. The Control Builder (CB) provides a default link
schedule of publications and function block execution phasing based on the function
block connections in the user configured control strategy. The basis for the link schedule
is this link's content from all currently loaded Control Modules (CM). Execution phasing
is based solely on function block existence in the CM. Order of execution is based on the
order in CM (ORDERINCM) parameter for each block. Publications are based on inter-
device function block connections and device to Experion system or Experion system to
device function block connections. The following publication rules apply.
Function block publications appear in the link data transfer schedule in the order
specified by their ORDERINCM parameters. (Duplicate values of ORDERINCM
may produce indeterminate ordering of those blocks involved.)
66
Experion PKS Series A Fieldbus Interface Module User's Guide
Honeywell
R400
July 2010
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