User manual

4.25. Ethernet Controller
A Davicom DM9000A 10/100 MBit Ethernet Controller is implemented on the Stamp Adaptor Board. It
serves as a reference Design and a 10/100 MBit Twisted-Pair Magnetic Module (transformer plus
filter).
Software drivers are available for the DM9000A for Linux 2.4/2.6 and Windows CE 4.2/5.0/6.0.
a) MAC Address
An individual 48-bit MAC address (Ethernet hardware address) is allocated to each Stamp9261. This
number is stored in flash memory as a U-Boot parameter. It is recommended not to change the MAC
address in order to comply with the IEEE Ethernet standards.
b) Layout considerations
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).
c) Ethernet LEDs
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).
- 22 -