GATEWAY CHIPS
MCUs with a pair of network interfaces run the gamut from Ubicom's low-cost IP3023 wireless network processor, which can handle six networks (see "Multi-Threading Hardware Revs Up Internet Edge Processors," April 14, p. 46), to NEC's 400-MHz, 64-bit Vr7701 processor with a pair of 10/100Base Ethernet interfaces. These MCUs can handle residential gateway and set-top-box applications with ease. A number of MCU vendors now deliver solutions in this area. Ethernet-to-Ethernet gateways remain popular in the SOHO environment. But in terms of shipment, CAN-to-CAN gateways lead Ethernet because they sit inside most automobiles.
Bridge applications constitute the other area where MCUs are getting play. In these applications, different networks are linked together. CAN-to-LIN bridges, like Mitsubishi Electric's M16C line, infuse automotive environments that may incorporate multiple bridges to isolate different parts of a car's electronics (Fig. 2).
Today, Ethernet-to-I2C and Ethernet-to-SPI are virtually indigenous within computer-systems management. Similar CAN devices are popular in the process-control environment. Examples include Microchip's line of PIC MCUs and Hitachi's H8 line with CAN 2.0b and support for either an SPI or I2C network.
There are even unique devices like the Lantronix Xport, which uses the x186-based DSTni LX MCU with built-in Ethernet that bridges serial devices. The entire system fits inside an extended RJ45 jack.
EMBEDDED WIRELESS
Certainly nowadays, wireless networking prevails, but integration with MCUs has yet to take place. Popular wireless solutions such as 802.11, Bluetooth, and ZigBee (802.15) all require major chunks of hardware outside of the MCU. Network protocol support is on the same order as Ethernet, making them more difficult to incorporate into small networks. ZigBee looks to be the easiest to incorporate into an MCU because of its slower operation, low power requirements, and simplified protocol.
Residential gateways, especially those that are wireless, require a bit more security than an isolated, embedded network. This is why chips like IDT's RC32365 incorporate encryption hardware. Designed to provide VPN (virtual private network) support, the MCU also includes a pair of Ethernet MACs (media access controllers) and an SPI.
Distributed embedded solutions are now easy to construct with MCUs that incorporate most, if not all, the hardware needed for one or more networks. Choosing the right network may be a more difficult task, but at least a sizable range of options is available.