Select the right network connection for your MCU-based M2M app

By Jason Wang and Harvey Jan
ASIX Electronics

Owing to its ease of use, low cost, high bandwidth, stability, security and compatibility across devices, Ethernet has become the de facto standard of network access for 32-, 16- and even 8bit MCUs, surpassing that of both SOHO and enterprise networks and expanding into the consumer electronics market.

The proliferation of machine-to-machine (M2M) communications anticipates a rise in Ethernet-capable MCU market. The question is, which is the best way for you to add this connectivity?

Eight embedded Ethernet solutions
There are eight distinct configurations to embed Ethernet based on the I/O interface (Figure 1). The designer chooses the appropriate configuration based on the interface needs of the target application.

The first three scenarios feature an MCU with an integrated network controller; of these, the first scenario features the highest degree of integration. The remaining scenarios (four through eight) do not feature an integrated Ethernet controller, and are able to interface with an external network controller through a serial (i.e. USB host) or parallel (i.e. PCI or non-PCI local bus) interface.

The first configuration in Figure 1 was once only possible with 16bit and 32bit MCUs, but the technological advances of the 8bit MCU has allowed it to capture more of the market with smaller form factors and higher integration. Applications that once required a 32bit MCU can now be powered by lower-cost, highly integrated and higher-capacity 8bit network MCUs.

The second scenario is divided into 8-, 16- and 32bit MCUs; the third scenario is dominated mainly by 16bit and 32bit MCUs. The fourth and fifth scenarios, which use a PCI Bus, and the eighth scenario, which uses a USB host, are serviced by high-end 32bit MCUs, while the sixth and seventh scenarios, which use a Non-PCI bus, are able to be controlled through 8-, 16- and 32bit MCUs.

The following elaborates on the three types of solution depicted in Figure 1: The non-PCI solution, the USB solution and the more powerful single-chip solution.

Figure 1. Which embedded Ethernet solution is right for your design?

Networking with a non-PCI MCU
The configuration in Figure 2 targets embedded systems without a PCI-bus but featuring a non-PCI or SRAM-like interface. This design can embed a MAC and PHY layer in the Ethernet controller to provide network access, such as the eighth scenario in Figure 1. Since the majority of MCUs provide the non-PCI local bus, this can provide a single-port network capability.

Figure 2. Monitor, control or access your device over the Internet using non-PCI Ethernet controller.

This solution is suitable for home appliances, industrial and home automation, security systems, remote management, streaming media and high bandwidth networking. Figure 3 depicts some of these applications: point-of-sale (POS) devices, wireless access points, broadband routers, IP phones, media sharing hosts, IP STBs, IP cameras, network storage, digital video recorders, DVD players, HDTVs, digital media hubs, game consoles, IPTVs, etc.

Figure 3. These are applications for an MCU with non-PCI Ethernet controller.

Networking using a USB Host
Figure 4 depicts the configuration for MCUs with a built-in USB host with either an internal or external USB to LAN controller, such as the eighth scenario in Figure 1. This configuration converts USB 2.0 to Fast Ethernet/Gigabit Ethernet in the embedded system through a cradle, port replicator or a docking station.

Because USB 2.0 only requires four pins, this allows the non-PCI bus to decrease the pin-count between the embedded system and the cradle or docking station. An alternative configuration uses a built-in USB host in combination with an external USB-to-LAN dongle to provide Ethernet access.

Figure 4. This is an application diagram of an MCU with USB-to-LAN controller.

The rationale behind this configuration is simple: to take advantage of the USB's "plug-and-play" convenience and the 4-pin serial bus's high 480Mbit/s data transfer rate. This configuration is suitable for computer peripherals, handheld devices, home appliances, streaming media, multimedia networking and consumer multimedia devices.

Figure 5 below depicts some of these devices, including USB Ethernet dongle, USB WiMAX card, ultramobile PC (UMPC), laptop docking station, cradles, digital recorders and players, DVD players, portable media players, IP STBs, game consoles, IPTV's and USB KVM Ethernet switches.

Figure 5. These are applications for an MCU with USB-to-Ethernet controller.

Single-chip MCU networking
Figure 6 depicts an embedded system that integrates the MCU, flash memory and both MAC and PHY in a single chip configuration with the smallest form factor, as described in the first scenario depicted in Figure 1.

This configuration is suitable for home appliances, industrial and home automation, security systems, remote management and streaming media applications such as POS devices, vending machines, IP cameras, Internet radio, automatic meter reading, environmental monitoring systems, network sensors, networked UPS, serial to Ethernet adapters and Ethernet ZigBee bridges.

Figure 6. Here's a network MCU connecting directly to the Internet.

Satisfying market demands for miniaturization
Embedded system designers are frequently faced with the dilemma of designing a remote management or communication device with higher specifications and functionalities without increasing its form factor. Chip vendors have provided a variety of solutions to this dilemma, one of which is by choosing a small package size.

Figure 7. These are embedded Ethernet solutions.

The 64-pin or TFBGA package depicted in Figure 7 allows the Ethernet chip to be a quarter of the size of a U.S. dime coin. An alternative solution is to incorporate a higher degree of integration in a single chip.

Figure 7 depicts one such chip that integrates Ethernet MAC/PHY, TCP/IP accelerator and flash memory into a single small form factor Ethernet MCU SoC.

The three scenarios described above offer alternative solutions to embedding Ethernet to satisfy the different needs for application designers today, whether they use a non-PCI interface, USB interface or single-chip solution.

About the authors
Jason Wang is director of marketing at ASIX Electronics. He can be reached at jasonw@asix.com.tw. Harvey Jan is director of R&D at ASIX Electronics. He can be reached at harvey@asix.com.tw.