Selecting the right network connection for your MCU-based machine-to-machine application

The proliferation of M2M communications anticipates a rise in Ethernet-capable microcontroller 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 input/output interface (Figure 1 below). The designer chooses the appropriate configuration based on the interface needs of the target application.

The first three scenarios feature a microcontroller 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.

Figure 1. Which Embedded Ethernet Solution is Right for Your Design?

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

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

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.

Networking with a Non-PCI Microcontroller
The configuration in Figure 2 below 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 microcontrollers 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 below depicts some of these applications: POS (point of sale) devices, wireless access points, broadband routers, IP phones, media sharing hosts, IP set top boxes, IP cameras, network storage, digital video recorders, DVD players, hi-definition televisions, digital media hubs, game consoles, IPTVs, etc.

Figure 3. Applications for MCU with Non-PCI Ethernet Controller

Networking using a USB Host
Figure 4 depicts the configuration for microcontrollers 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 4 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. Application Diagram of 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 480Mbps 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, UMPC (ultra-mobile PC), laptop docking station, cradles, digital recorders and players, DVD players, portable media players, IP set top boxes, game consoles, IPTV's and USB KVM Ethernet switches.

Figure 5. Applications for MCU with USB-t0-Ethernet Controller

Single Chip Microcontroller Networking
Figure 6 below depicts an embedded system that integrates the microcontroller, flash memory, and both MAC and PHY layers 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. Network MCU Connecting Directly to the Internet

Satisfying the 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. Embedded Ethernet Solutions

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

Figure 7 (right, bottom) depicts one such chip that integrates Ethernet MAC/PHY, TCP/IP accelerator, and Flash memory into a single small form factor Ethernet microcontroller 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.

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. He can be reached at: harvey@asix.com.tw