Components that use buffered data

Subscribing to the Buffer property

Attribute

User defined attributes with I/O configured to read or read/write data can support buffered data processing.

When buffered data is enabled, the attribute subscribes to the buffer property and receives the buffered data via Message Exchange. See Message exchange and attributes for more information about Message Exchange.

Scripts

A script subscribes to an attribute and receives buffered data from it. A specific syntax is used to properly process buffered data in scripting. Scripts can also read the buffer from an attribute or directly from the DIObject.

For more information, see Use scripts to process buffered data.

Processing buffered data

Communication Drivers

Communication Drivers collect and store VTQ data from field devices. Communication Driver functionality is unchanged by the buffered data feature. Protocol interfaces within the servers allow buffered data from the field devices to be processed. Communication Drivers, in turn, can pass the buffered data as packets to the Application Engine.

Telemetry Server

The Telemetry Server collects and stores VTQ data from RTUs (remote terminal units) connected to field devices. The Telemetry Server typically only sends data to Application Server when polled. Since polling may be performed only periodically, there may be a large dataset of intermediate values that would be lost if buffering is not enabled.

DIObject

For attributes with a buffer property that is being subscribed, the DIObject (Data Integration Object) collects VTQ values from Communication Drivers, and packs the VTQ values into buffer collections, based on scan cycle completion or on end of data received. Typically, the PLCClient object is used for data integration.

Application Engine

The Application Engine hosts and executes the ApplicationObjects’ logic.

Data Consumers

When buffered data is enabled, data consumers such as the Historian and alarms subsystems subscribe to the Buffer property of the configured attribute to receive published buffered data. The buffered data, a stream of VTQs, is assembled and appended in caches to avoid data folding, and is then published through Message Exchange to consumers such as the Historian, alarms and scripts. See Message exchange and attributes for more information.