The EM510 has three LED control lines — SG, SR, SE. All lines have the same internal structure and the LEDs should be connected as shown on the schematic diagram below. The maximum load for each line is 10mA. For a small LED, a 330 Ohm series resistor will provide sufficient brightness.
The SG and SR lines are used to control two status LEDs found on Tibbo products. These LEDs can show various flashing patterns indicating the current device state (see Status LEDs). On the EM510, there is an added twist: the same pair of status LEDs also indicates the current Ethernet link status through LED brightness. We refer to the EM510's status LEDs as "dual-function LEDs." This is a patented featured available exclusively on our MiniMo (R) devices. Here is how this works:
When a "live" Ethernet cable is not plugged into the RJ45 jack, flashing patterns displayed by the status LEDs are "dimmed". That is, LEDs turn on at around 20% of their nominal brightness. When a "live" Ethernet cable is plugged into the RJ45 jack, flashing patterns are displayed at full brightness.
This dual functionality was designed into the EM510 for an important reason: Many popular RJ45 jacks have two internal LEDs. With the EM510, it is possible to use these LEDs both for the module state indication, and for Ethernet link indication. This eliminates the need for any additional LEDs.
The third LED control line — SE — is a separate line for Ethernet link indication. The SE LED will be on when the Ethernet interface is in the linked state.
There is no indication of the Ethernet link speed on the EM510.