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CompoNet and DeviceNet


Objectives
This Technical Note aims to give a brief overview of both CompoNet and DeviceNet.
Introduction
The evolution of CIP field networks.
In 2006, Omron and ODVA launched a new field network standard into the world of industrial automation: CompoNet.
Based on the Common Industrial Protocol (CIP) as used in EtherNet/IP and DeviceNet, its target is to complete a seamless networking architecture from plant level to sensor/actuator level. This had not previously been possible with EtherNet/IP and DeviceNet alone.
Content
One connection to any device
One of the main reasons in developing CompoNet was to simplify the setup, commissioning and maintenance of automation systems. As field devices like sensors and drives become more sophisticated, the need to set up parameters, monitor and tune their behaviour, and keep track of their status becomes increasingly complex. A few hundred parameters per device is no longer an exception.
Networks linking such field devices to the control system must support fast and reliable cyclic data exchange as well as acyclic message communication. When multiple production cells are linked at a higher level, a common messaging protocol will allow access to the device data from anywhere in the network. It will no longer be necessary to walk from cell to cell, or even from device to device, to plug in and inspect and correct settings. Machines and production lines can be managed from a single connection.

Simplicity and Speed
Surely this was already possible by using DeviceNet as field network. But as the number of field devices on the network increases, and both cyclic and acyclic traffic grow, the network performance will drop. DeviceNet allows some fine-tuning of the communication per device, e.g. by only transferring data on change of state, but the penalty is additional effort in the configuration and commissioning stage. The strength of CompoNet is combining ease of setup, fast and reliable cyclic communication and CIP-based messaging in one
network. Simplicity is achieved by a restricting CompoNet to single-master operation, and limiting the total amount of input and output data to 80 words per direction.

This results in strict timing with fixed cycle times as little as 1 ms per 1000 I/O points. Messaging is bandwidth-restricted, giving priority to cyclic communication. By using non-shielded 2-wire cable, CompoNet installation is quick and cheap. Even more installation time can be saved by using the standard unshielded flatcable and IDC connectors. This will also minimise the chance of mis-wiring, reducing
commissioning time. And by network segmentation, using repeaters, step-by-step commissioning and troubleshooting you can shorten the initial setup of new installations considerably.

Freedom of layout
The next problem tackled by CompoNet is network topology. Most field networks leave little choice: line or ring structures require the network cable to run along all stations in sequence. Each device has two connecting lines, one to and one from the device. For wide-area applications with many small nodes, like warehouses or conveyor lines, CompoNet offers a low-speed mode with free topology. Unrestricted branching with a total line length per segment of 500 m can make wiring much more efficient. And with up to 63 repeaters per network (max. 3 layers deep), very wide ares can be covered with a minimum of cable.
DeviceNet has a large installed base worldwide, and a large range of products on the market. It will still be an efficient network because of its configurability and large data capacity. But CompoNet will provide a simpler and faster solution for machine automation, and a more economical and easy-to maintain solution for small node distribution. All the while offering seamless access to every device.
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Created 2008-12-02
Modified 2008-12-04
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