USB MultiSwitchTM Hub

Datasheet

8.3Host Ownership and Port Speed LED Indication:

All 8 LED pins are used in this mode in conjunction with 8 Dual-color LEDs (each LED pair in a single package) to indicate which upstream Host owns each specific downstream Port, as well as the speed that the downstream device is operating at.

Each dual-color LED provides two separate colors (commonly Green and Red). If each of these separate colors are pulsed on and off at a rapid rate, a user will see a third color (in this example, Orange). By this means, 4 different “color” states are possible (Green, Red, Orange, and Off).

3.3V

LED pin

General

Purpose

Diode

Connect to other dual color diodes.

Green LED

Current limiting resistor

Red LED

Figure 8.1 Dual Color LED Implementation Example

Figure 8.1 shows a simple example of how this LED circuit will be implemented. The Circuit will need to be replicated for each of the 8 LED pins on the USB2524. 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 1KHz 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 or Red LED will light up, this is the “Off” state.

SMSC USB2524

45

Revision 1.91 (08-22-07)

 

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