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Interrupting processing
• TheActivitycanfinishprocessingtheitempriortoshuttingdown,suchaswhentheshut- down is part of scheduled maintenance and can wait until the item is finished.
Items that are not discarded leave through the Activity’s normal item output.
SD output connector
The Activity block’s variable output connection contains an SD connector that can be used to relay shutdown status. Depending on how the Activity has been configured, this connector either outputs a 1 (one) while the Activity is down and a 0 (zero) when it is up, or it outputs the number of items that are currently shutdown. If a value connection has been made to the SD input, the SD output connector is set to 1 or 0; if an item connection has been made to the SD input, the SD output connector reports the number of items currently shutdown.
Scheduled Shutdown model
The Create block is often used to schedule an Activity to shut down. For example, the Sched- uled Shutdown model schedules downtime for a machine by connecting a Create block’s item output to the SD input on an Activity.
Scheduled Shutdown model
The “Shutdown Schedule” from the
Create block’s Shutdown tab is cloned
onto the model worksheet and shown at
right. It indicates that two items will be
created, one at time 2 and one at time 7.
Each item has a downTime attribute as
seen at the top of the fourth column; the attribute’s value is 2.5 for the first item and 1 for the second item. In the Create block’s dialog, this maintenance schedule has been set to repeat every 10 time units.
The Activity block is set to process one item at a time. Its Shutdown tab, shown at right, indicates that all items currently in processing will be shutdown when a “shutdown item” is received at SD, downTime is the name of the attribute that determines the duration of
Settings in Activity block
Schedule in Create block
Discrete Event

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