Electronic Design

ARCNET, The Engineer's Secret Weapon

ARCNET is one of the best-kept secrets in the world of embedded systems. You may run into ARCNET technology when you ride a train or drive a car, play a multiplayer racing arcade game or slot machine, or use a copier or ATM. You can find ARCNET used in European windmills, power-generation equipment in China, Japanese industrial robots, and wireless basestations in the U.S. You may be surrounded by ARCNET while on the bridge of a boat that uses cutting-edge navigation devices, in a hospital room full of medical equipment, or in a new building with automated HVAC controls. ARCNET is everywhere, but most people don't even know it.

So what makes ARCNET popular? Like Ethernet, ARCNET is a networking technology with a long track record that has successfully transformed itself over the years to meet the specific needs of its customers. Unlike Ethernet, ARCNET is based on a very simple token-passing protocol, making it much more attractive for embedded system designers looking for a robust, easy to use communication technology that requires little or no software to implement.

ARCNET provides the utmost in flexibility. With an array of transceivers to choose from, system designers can select the perfect match for their system performance and cost requirements. ARCNET nodes can be connected in bus, star, or mixed topologies, allowing the system designer to minimize wiring costs and overcome physical wiring layout barriers. ARCNET also gives system designers a lot of options for message packet sizes. Having no minimum packet size, unlike Ethernet, ARCNET can send from 1- to 507-byte messages.

Another reason why ARCNET is so well liked is that the communication protocol is embedded in hardware. This means that embedded system designers don't need to develop or purchase additional software, reducing development time and cost. Without software running the communication protocol, ARCNET doesn't burden the host microcontroller (MCU) and has an effective throughput that is much higher than other technologies—such as Ethernet, which depends on the MCU to process software stacks. Embedded systems designers can thus maintain low MCU costs.

The ARCNET protocol also contains features, such as flow control, that normally have to be implemented using software. Built-in flow control at the data link layer is rare. This feature prevents an MCU from being swamped with messages. Ethernet does not have it.

ARCNET's deterministic nature is perfect for applications where the network behavior has to be extremely predictable. In addition, ARCNET's support of communication throughput of up to 10 Mbits/s is more than sufficient for most embedded application requirements. Embedded system designers also find ARCNET's plug-and-play feature attractive. It allows nodes to be taken out or added to an ARCNET network on-the-fly.

ARCNET controllers have small footprints, coming in 48-pin packages, and are priced competitively. They're designed with a flexible interface that will connect to all MCUs and requires minimal MCU and media interface logic. The flexible, easy to use aspects of ARCNET have created over 1500 users and 11 million nodes sold to date, as well as many die-hard fans.

Why don't more people know about ARCNET? Many embedded systems engineers find ARCNET appealing as a base for their own proprietary embedded network, which they tend to brand with a different name. In fact, ARCNET is a great solution for companies that need an embedded networking solution, don't want to start from scratch, and want something simple to use. Because companies value the secure aspects of a closed ARCNET embedded network as opposed to an Ethernet-based system where intruders can more easily tap in and sniff for TCP/IP packets, the more they can keep ARCNET a secret, the better.

So if you're looking for a networking solution that's simpler to use than Ethernet and has higher performance than CAN, ARCNET is the answer. The secret is out.

TAGS: Robotics
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