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Chapter 4. How Do I? 29

See Also

Overview: Creating Datablocks Inside FIX/iFIX Applications

Configuring a Driver for Demand Polling

By entering a special I/O address in a Digital Output or Analog Output block, you can

poll:

• Individual datablocks.

• Devices and all their datablocks.

• Channels and all their devices and datablocks.

This one-shot poll is called a demand poll. You may want to set your driver up for

demand polling if:

• The driver’s poll time is slow and you want to get data without having to wait

for the next update.

• You want to poll a device after opening a FIX/iFIX operator display.

• You want to poll a device just before generating a report.

The poll occurs when you write a value to the block.

The I/O address syntax is: !POLL: NAME

where NAME is the name of the datablock, device, or channel you want to demand

poll.

Using demand polling does not affect the configured poll rate of the datablock. For

example, if you demand poll a datablock 15 minutes into a 30-minute scan cycle, the

driver polls the datablock again 15 minutes, as originally scheduled.

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