The Xentara Modbus Driver v1.2
User Manual
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Polls are a type of Xentara I/O transaction.
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.
Modbus polls have the following members:
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”. |
execute | Executes the poll and updates the values of the attached channels. |