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Datasheet
Revision 1.91 (08-22-07) 44 SMSC USB2524
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.
8.1 USB 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
8.2 Basic 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.