Electronic Design

Single-Chip Networking

Cutting the bill of materials (BOM) usually means trimming the number of chips and components. One may be "the loneliest number," but a single-chip solution is the goal of most designers—especially when it comes to networking.

To that end, designers are starting to exploit Power-over-Ethernet (PoE). PoE is suitable for powering Ethernet-equipped microcontrollers like Freescale's 16-bit MC9S12NE64 (see "Building A One-Chip Web Server," ED Online 9115), a two-chip solution using Microchip's ENC28J60 (see "Mini Ethernet Chip Contends In Low-End Networking Space," ED Online 10118) SPI-based Ethernet controller, or Digi's 32-bit NS9360 (see "Single-Chip Network MCU Handles Java/DSP Chores," right) targeted at a multi-chip module solution.

Today, designers have more choices than ever for pruning a networked solution down to the bare minimum. A number of 16- and 32-bit MCUs incorporate a 10/100 Ethernet media-access controller (MAC) and physical layers. Some 32- and 64-bit high-performance MCUs integrate one or more Gigabit Ethernet MACs.

Developers also can choose from a wide range of networking stacks. Likewise, these solutions typically have low-cost development kits like those I've reviewed in my EiED Online column. The kits let developers get up and running in days instead of weeks or months.

Don't rush off too quickly with Ethernet. Your application may benefit from controller-area-network (CAN) MCUs. CAN's limited packet size (8 bytes) and slower data rate (1 Mbit/s) may be just the ticket if the average message rate is about 7000 messages/s. While Ethernet has concentrated on CAT5 and fiber, CAN supports a wider range of cabling options. Its broadcast-oriented nature can be more efficient than Ethernet in many applications. The cost of CAN MCUs is low because they're used in most automobiles. And, CAN/Ethernet MCUs provide single-chip gateway solutions.

On the wireless side, 802.11 remains a two-chip solution. The expense and ever-changing nature of the wireless world makes it difficult to nail down a specification for a single-chip, 802.11 MCU. It may be another two years before this type of chip becomes available.

On the other hand, ZigBee likely will have one or more single-chip solutions before the year is out. Two-chip solutions are the norm because they take advantage of the plethora of MCUs and because vendors have not finalized the type of feature set the integrated MCU will contain. The cost of these chips will prevent the wide selection of options currently available with MCUs, but expect to see more than one alternative per vendor.

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