USB MultiSwitchTM Hub

Datasheet

Chapter 8 LED Interface Description

The USB2524 supports 3 different (mutually exclusive) LED modes. USB Mode provides 8 LEDS, which conform to the USB 2.0 specification functional requirements for Green and Amber LED’s. Basic Host Owner LED Indication mode uses 8 Single color LED’s to provide user indication of upstream host ownership of the 4 downstream ports. Host Owner and Downstream Port Speed LED Indication mode uses 8 Dual Color LED’s to provide both a User indication of Downstream port ownership, while simultaneously displaying an indication of the speed of the downstream device which is attached to each of the downstream ports.

8.1USB Mode:

The LED_A[4:1]_N pins are used to provide Green LED, and LED_B[4:1]_N pins are used to provide Amber LED support as defined in the USB 2.0 specification. The USB Specification defines the LED’s as port and error status indicators for the downstream ports. Please note that no indication of upstream host ownership is possible in this mode. The pins are utilized as follows:

LED_A1_N = Port 1 Green

LED_B1_N = Port 1 Amber

LED_A2_N = Port 2 Green

LED_B2_N = Port 2 Amber

LED_A3_N = Port 3 Green

LED_B3_N = Port 3 Amber

LED_A4_N = Port 4 Green

LED_B4_N = Port 4 Amber

8.2Basic Host Owner LED Indication:

All 8 LED pins are used in this mode in conjunction with single-color LEDs to indicate which upstream Host owns each specific downstream Port. The usage and assignment is as follows:

LED_A1_N = Port 1 Owned By Host A

LED_B1_N = Port 1 Owned By Host B

LED_A2_N = Port 2 Owned By Host A

LED_B2_N = Port 2 Owned By Host B

LED_A3_N = Port 3 Owned By Host A

LED_B3_N = Port 3 Owned By Host B

LED_A4_N = Port 4 Owned By Host A

LED_B4_N = Port 4 Owned By Host B

If a Port is disabled, or is Unassigned, then neither the “A” or “B” LED associated with that port will be asserted.

Since these LED’s are provided to give an end-user a clear indication of Host Ownership of downstream ports, they will function when the hub is in suspend, and will indicate Host ownership even if the applicable assigned Host is disconnected, powered off, etc.

Revision 1.91 (08-22-07)

44

SMSC USB2524

 

DATASHEET