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USB 2.0 Hi-Speed 7-Port Hub Controller
Datasheet
Revision 2.8 (09-17-12) 18 SMSC USB2517
DATASHEET
Figure 6.1 Dual Color LED Implementation Example
Figure 6.1 shows a simple example of how this LED circuit will be implemented. The circuit should be replicated for
each of the 7 LED pins on the HUB. In this circuit, when the LED pin is driven to a logic low state, the Green LED
will light up. When the LED pin is driven to a Logic High state the Red LED will light up. When a 1 KHz square wave
is driven out on the LED pin, the Green and Red LED's will both alternately light up giving the effect of the color
Orange. When nothing is driven out on the LED pin (i.e. the pin floats to a "tri-state" condition), neither the Green
nor Red LED will light up, this is the "Off" state.
The assignment is as follows:
LED_A1_N = LED D1 (Downstream Port 1)
LED_A2_N = LED D2 (Downstream Port 2)
LED_A3_N = LED D3 (Downstream Port 3)
LED_A4_N = LED D4 (Downstream Port 4)
LED_A5_N = LED D5 (Downstream Port 5)
LED_A6_N = LED D6 (Downstream Port 6)
LED_A7_N = LED D7 (Downstream Port 7)
The usage is as follows:
LED_Ax_N Driven to Logic Low = LS device attached (Green LED)
LED_Ax_N Driven to Logic High = FS device attached (Red LED)
LED_Ax_N Pulsed @ 1 KHz= HS device attached (Orange color by pulsing Red & Green).
LED_Ax_N is tri-state= No devices are attached, or the hub is in suspend, LED's are off.