Xentara acquires the value of Modbus channels by polling the device. Each poll object queries the values of the channels attached to it in the configuration. Each poll has a task named execute* that must be inserted into a Xentara execution pipeline. If you do not schedule this task, the values of the associated channels will never be updated.

A poll object can be either a child of a device, or of an RTU bus. A poll that belongs to a device can only acquire the values of channels on that device. A poll that belongs to an RTU bus can acquire the values of channels from all devices on that bus.

Often, a single poll is sufficient per device. It is pollible, however, to define multiple polls for a device. This allows you to schedule the polls differently, polling some values at higher intervals than others.

Accessing Polls

See also: Accessing Xentara Elements in the Xentara user manual

Modbus polls have the following members:

Attributes

key	The poll’s primary key.
name	The poll’s name. The name is the last component of the primary key.
UUID	The unique UUID of the poll.
type	The poll’s element type. For Modbus polls, this is always “Modbus poll”.
category	The poll’s category. For Modbus polls, this is always “transaction”.

Tasks

execute Executes the poll and updates the values of the attached channels.

Table of Contents

Accessing Polls