EM203 Ethernet-to-Serial Module


The EM203 is an Ethernet module for onboard installation. Module hardware includes one auto-MDIX* 10/100BaseT Ethernet port (standard Ethernet magnetics are NOT integrated into the module), one CMOS-level serial port, and an internal processor, whose firmware acts as a bridge between the Ethernet and the serial port. The Ethernet "side" of the module connects to the RJ203 jack/magnetics module , a standard Ethernet magnetics circuit (such as YCL-PH163112) or RJ45 connector with integrated magnetics. Serial "side" interfaces directly to the serial port pins of most microcontrollers, microprocessors, UARTs, etc. The module additionally features four status LEDs onboard.

The EM203 device is an improved version of the EM203A module. The EM203 uses newer DM9000B Ethernet controller, which features auto-MDIX as well as fully digital PHY. Additionally, the EM203 has lower profile due to the removal of two large crystal oscillators which are present on the EM203A and are mounted vertically. The oscillators on the EM203 are tiny SMT components.

From the hardware standpoint, the EM203 can be viewed as a universal platform suitable for running a variety of applications. It is the application firmware, not the hardware that gives the EM203 most of its functionality. The EM203 is offered with two distinctively different kinds of application firmware ( version restrictions apply -- see below ):

"Serial-to-Ethernet" firmware, currently in its 3rd generation ("Release3"), turns the EM203 into a ready-to-work serial-to-Ethernet converter that can connect almost any kind of serial device to the Ethernet (TCP/IP) network. This firmware has fixed functionality; you adjust the way the EM203 behaves by specifying the values of programmable parameters (settings) defined in this firmware.
TiOS (Tibbo Operating System) firmware turns the EM203 into a BASIC-programmable controller. When running TiOS, the EM203 has no pre-defined functionality -- it is your BASIC application that defines what the EM203 will do. TiOS and BASIC programming are covered in a separate Manual ("TAIKO Manual").


Firmware version restrictions

The use of the newer DM9000B Ethernet controller required firmware changes which were made in V3.70 of the "serial-to-Ethernet" firmware and 2.05.10 of the "TiOS" firmware. Earlier firmware versions will not run on the EM203! If you have to stick to the older firmware, please use the EM203A device instead.

The application firmware of the EM203 can be upgraded through the module's serial port or Ethernet port. Serial upgrades are facilitated by a so-called Monitor - a fixed "service" firmware inside the EM203. Network upgrades rely on the application firmware, that is, the firmware can "upgrade itself".

The EM203 is supplied with "serial device server" firmware pre-loaded. If you wish to receive the module with TiOS firmware, please specify option "P" device on your order. Alternatively, you can just load the TiOS firmware by yourself. Current firmware versions are posted on our website.


The EM203 module features a heat-conductive sticker. Protective paper of the sticker MUST BE REMOVED prior to installing the module onto the host PCB. More on this in the Thermal Considerations topic.

* Auto-MDIX means automatic detection of "straight" and "cross" cables.