Xentara reads and writes the values of the different sub-units of a card using a sub-unit handler object. Each handler object reads and writes the values of the sub-units attached to it in the configuration. The handler has two tasks named read and write that must be inserted into a Xentara execution pipeline. If you fail to schedule the read task, the values of the associated sub-units will not be updated. If you fail to schedule the write task, modified values for the associated sub-units will not be written back to the PXI module. Each sub-unit handler object must be a child element of the card whose sub-units it handles.

Often, a single handler is sufficient per card. It is possible, however, to define multiple handlers for the same card. This allows you to schedule the handlers differently, reading and/or writing some values at higher intervals than others.

Accessing Sub-Unit Handlers

Pickering PXI sub-unit handlers have the following members:

Attributes

key	The handler’s primary key.
name	The handler’s name. The name is the last component of the primary key.
UUID	The unique UUID of the handler.
type	The handler’s element type. For sub-unit handlers, this is always “Pickering PXI sub-unit handler”.
category	The handler’s category. For sub-unit handlers, this is always “transaction”.

Tasks

read	Reads the values of the attached sub-units from the physical PXI module.
write	Writes any pending modified values of the attached sub-units back to the physical PXI module.

Scheduling Handler Tasks

See also: Scheduling Tasks in the Xentara user manual

All tasks for all sub-unit handlers belonging to a single card card must be scheduled within the same execution track. Additionally, none of these tasks must be scheduled in parallel pipeline segments within their pipeline.

Table of Contents

Accessing Sub-Unit Handlers

Scheduling Handler Tasks