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 ControlNet Network


The Allen-Bradley ControlNet network is a state-of-the-art control network that meets the demands of real-time, high- throughput applications. The ControlNet network combines the functionality of an I/O network and a peer-to-peer network while providing high-speed performance for both functions.

The ControlNet network gives you deterministic, repeatable transfers of all mission-critical control data in addition to supporting transfers of non-time-critical data. The patented media-access method used on the ControlNet network results in deterministic delivery of time-critical (scheduled) data by assigning it a higher priority than non-time-critical (unscheduled) data. As a result, I/O updates and controller-to-controller interlocking always take precedence over program uploads and downloads and messaging.

The ControlNet network and products such as the ControlNet-to-DeviceNet Linking Device (catalog number 1788-CN2DN), help deliver solutions that integrate FOUNDATION Fieldbus devices and DeviceNet devices into a common, seamless architecture.

All devices on the ControlNet network have direct access to all data on FOUNDATION Fieldbus network. The ControlNet-to-FOUNDATION Fieldbus (H1) Linking Device (catalog number 1788-CN2FF) has many benefits:

- configuration of FOUNDATION Fieldbus devices from the ControlNet network
- two-way data sharing between ControlNet devices and FOUNDATION Fieldbus devices
- diagnostic feedback and monitoring of multiple FOUNDATION networks from a single ControlNet network
- centralized controllers on a ControlNet network control events on FOUNDATION Fieldbus networks

Flexible installation options for the ControlNet network include:

- Redundant Media Option helps ensure that a system can maintain operation during a cable fault condition
- Intrinsic Safety Option lets you install a ControlNet network in hazardous, explosive locations. The combination of a ControlNet 1786 fiber hub and a ControlNet Ex 1797 fiber hub allows for flawless high-speed deterministic data flow and messaging between hazardous and safe areas. This combination functions as an intrinsically-safe isolator between hazardous and safe areas and can provide long-distance communication.

Functional Design

The ControlNet network is simple and cost-effective to install, and offers you flexible installation options. A-B offers PLC processors with built-in ControlNet scanners, ControlNet adapters for I/O chassis, and ControlNet computer interfaces for personal computers. Although the ControlNet network is based on bus technology, you can use repeaters to implement tree and star topologies. You can also install optional redundant media. The ControlNet processors include ports that let you share data between a ControlNet network and your already installed Data Highway Plus and Universal Remote I/O networks.
Types of devices that communicate on the ControlNet link include: controllers, I/O, MMIs, PCs, drives, coordinated drive systems, weld control, motion control, vision systems, transducers, and valve manifolds.

Mechanical Design

The ControlNet network transfers scheduled data at 5M bit/s, which improves both I/O performance and processor-to- processor communication. Its flexible control system architecture can work with multiple processors, and you can install up to 99 addressable nodes (via taps) anywhere along the trunk cable of a ControlNet link. There is no minimum tap separation, and you can access the ControlNet network from every node (including adapters).


The ControlNet network provides the functions of the A-B Data Highway Plus and Universal Remote I/O networks at a 5M-bit/s rate. Multiple processors can each control their own assigned outputs on a single common ControlNet link and to each monitor all inputs on the link. Any processor on the link can send a message to any other processor on the link.
Messages from a node on one ControlNet link can be routed through the ControlLogix gateway to a node on either another ControlNet link, a DeviceNet link, a DH+ link, or an Ethernet link.

ControlNet I/O

In addition to accommodating the high ControlNet data transfer rate and a large number of I/O chassis, the ControlNet link provides a simple, deterministic, flexible means of transferring I/O data.
For I/O on a ControlNet link, you can implement both discrete and non-discrete transfers of I/O data:

- A discrete transfer of I/O data occurs when a single unit of I/O data (8, 16, or 32 bits that correspond to the module's I/O image) is transmitted to or received from each I/O module in the I/O chassis. With just one discrete transfer, you can update the I/O image for all of the modules in the I/O chassis.
- A non-discrete transfer of I/O data occurs when a block of data (64 words maximum in a single packet) is transferred to or from an I/O module.

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