USB2517 datasheet(17/58 Pages) MICROCHIP

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DS00001598B-page 17

USB2517/USB2517I

6.0

LED USAGE DESCRIPTION

6.1

LED Functionality

The hub supports 2 different (mutually exclusive) LED modes. The USB Mode provides 14 LED’s that conform to the

USB 2.0 specification functional requirements for Green and Amber LED’s. The LED Mode “Speed indicator” provides

the downstream device connection speed.

6.1.1

USB MODE 14-WIRE

The LED_A[7:1]_N pins are used to provide Green LED support as defined in the USB 2.0 specification. The

LED_B[7:1]_N pins are used to provide Amber LED support as defined in the USB 2.0 specification. The USB Specifi-

cation defines the LED’s as port status indicators for the downstream ports. Please note that no indication of port speed

is possible in this mode. The pins are utilized as follows:

• LED_A1_N = Port 1 green LED

• LED_A2_N = Port 2 green LED

• LED_A3_N = Port 3 green LED

• LED_A4_N = Port 4 green LED

• LED_A5_N = Port 5 green LED

• LED_A6_N = Port 6 green LED

• LED_A7_N = Port 7 green LED

• LED_B1_N = Port 1 amber LED

• LED_B2_N = Port 2 amber LED

• LED_B3_N = Port 3 amber LED

• LED_B4_N = Port 4 amber LED

• LED_B5_N = Port 5 amber LED

• LED_B6_N = Port 6 amber LED

• LED_B7_N = Port 7 amber LED

6.1.2

LED MODE SPEED INDICATION

The LED_A[7:1]_N pins are used to provide connection status as well as port speed by using dual color LED's. This

scheme requires that the LED's be in the same package, and that a third color is produced so that the user perceives

both LED's as being driven "simultaneously".

The LED_A[7:1] pins used in this mode are connected to 7 dual color LED’s (each LED pair in a single package). These

pins indicate the USB speed of each attached downstream device.

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). Using this method, 4 different

"color" states are possible (Green, Red, Orange, and Off).

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