3. Ethernet Controller

Please take care of the specific layout requirements of the Ethernet port when designing a base board. The two signals of the transmitter pair (ETX+ and ETX-) should be routed in parallel (constant distance, e.g. 0.5mm) with no vias on their way to the RJ45-jack. The same is true for the receiver pair (ERX+ and ERX-). No other signals should be crossing or get next to these lines. If a ground plane is used on the base board, it should be omitted in the vicinity of the Ethernet signals.

A 1nF / 2kV capacitor should be connected between board ground and chassis ground (which is usually connected to the shield of the RJ45-jack).

Two LED outputs from the DM9000A controller can be used on the base board. LED_S indicates the current speed of the Ethernet connection (100MBit = on, 10 MBit = off). LED_L indicates the combined link and carrier sense signal (LED mode 1 of the DM9000A), or only the carrier sense signal (LED mode 0).