Configure I/O as write-only

Select Write in the I/O parameters area. Define a Write to (output) destination by using I/O auto-assignment, by typing in the reference string, or by selecting the Attribute Browser button at the right.

• Use I/O auto-assignment to prepare the output destination for automatic assignment to a configured Device Integration (DI) object or other data source. For information about using I/O auto-assignment, see I/O auto assignment.

• If the OutputDest attribute is locked in the parent template, the attribute cannot be updated with the resolved reference when the object is deployed, and the runtime value will be "---Auto---".

• Use the Attribute Browser to select an attribute and automatically insert the correct reference string for that attribute. For more information about using the Attribute Browser, see Use the galaxy browser to reference objects .

Select the Output Every Scan check box if you want the attribute to write to the Destination attribute every scan period of the object. Otherwise, the write executes only when the value is modified or when quality changes from Bad or Initializing to Good or Uncertain.

Writeable and Calculated attributes can be configured with a Write I/O Feature. Arrays are not supported.

A Write I/O Feature can be added to a derived template or to an instance. If added to a template, the existence of the Write I/O Feature is automatically locked in derived objects. The output Destination attribute is separately lockable in templates.

If the data types of the configured and destination attributes are the same and only when the quality of the extended attribute is good, the two attributes are set to equal values according to the configured object’s execution rate. If the two attributes are different data types, coercion rules are applied. If coercion fails, the extended attribute is placed into a configuration error and type mismatch state.

An attribute that is enhanced with a Write I/O Feature has the following characteristics:

• A value can be output only when quality is Good or Uncertain. The quality is not output, only the value is output, because quality is not output on sets.

• When the quality changes from Bad or Initializing to Good or Uncertain, the value is output, even if the value is not modified.

• When the quality changes from Good to Uncertain, with no value modification, the value is not output.

• When the object goes Off Scan, no output is done.

• When the extended object is Off Scan, quality is always Good and user sets are accepted.