LEDs and LED Lines
The EM2001 has three LEDs onboard:
- The red and green status LEDs.
- The yellow Ethernet status LED.
Further information on status LEDs can be found in Status LEDs.
The EM2001 also has two control lines — SG and SR — for connecting to external green and red status LEDs. These external LEDs work in parallel with the onboard LEDs. Since the maximum sink current of an I/O line is 10mA and the onboard LEDs already consume around 7mA, externally connected LEDs must not consume over 3mA of current. Connect external SR and SG LEDS through buffers (logic gates) if higher current is desired. SG and SR lines are active low, i.e. an LEDs must turn on when its control line is at LOW. Take this into consideration when designing the LED circuit.
Your Tibbo BASIC/C application can control red and green status LEDs, as well as up to four externally connected LED pairs through the pattern (pat.) object, which is documented in the TIDE, TiOS, Tibbo BASIC, and Tibbo C Manual.