Why ControlNet?

From proprietary to public standard, the proliferation of industrial networks offers users various benefits, but unfortunately from different networks. Couple this with the flattening of architectures and demands for higher performance, and you can see there was a need for an automation and control network that combined the benefits of several networks onto one link for increased system performance. Also needed was a control network to reliably predict when data will be delivered and ensure transmission times are constant and unaffected by devices connecting to, or leaving, the network.

These realities drove the development of ControlNet ... a real-time, control-layer network providing for high-speed transport of both time-critical I/O data and messaging data, including upload/download of programming and configuration data and peer-to-peer messaging, on a single physical media link. Deterministic and repeatable, ControlNet's high-speed (5 Mbits/sec) control and data capabilities significantly enhance I/O performance and peer-to-peer communications.

Picture - The Media Access Control Method

ControlNet's Media Access Method Taking full advantage of the Producer/Consumer model, ControlNet allows multiple controllers to control I/O on the same wire. This provides significant advantage over other networks, which allow only one master controller on the wire. ControlNet also allows multicast of both inputs and peer-to-peer data, thus reducing traffic on the wire and increasing system performance.

ControlNet is highly deterministic and repeatable -- critical requirements for ensuring dependable, synchronized and coordinated real-time performance. Determinism is the ability to reliably predict when data will be delivered, and repeatability ensures that transmit times are constant and unaffected by devices connecting to, or leaving, the network. These features are further enhanced with user selectable I/O and controller interlocking update times to match application requirements.

ControlNet provides:

	Bandwidth for I/O, real-time interlocking, peer-to-peer messaging and programming - all on the same link
	Deterministic, repeatable performance for both discrete and process applications
	Multiple controllers controlling I/O on the same link
	Multicast of both inputs and peer-to-peer data
	Media redundancy and intrinsically safe options
	Simple installation requiring no special tools to install or tune the network
	Network access from any node
	Flexibility in topology options (bus, tree, star) and media types (coax, fiber, other)

How it works:

Network access is controlled by a time-slice algorithm called Concurrent Time Domain Multiple Access (CTDMA), which regulates a node's opportunity to transmit in each network interval. You configure how often the network interval repeats by selecting a network update interval (NUT). The fastest NUT you can specify is 2 ms.

Information that is time-critical is sent during the scheduled part of the NUT.

Information that can be delivered without time constraints (such as configuration data) is sent during the unscheduled part of the NUT.