USB 2.0 to 10/100 Ethernet Controller
Datasheet
Chapter 7 NetDetach Operation
NetDetach operation is supported only by LAN9500A/LAN9500Ai
.
NetDetach is a mode of operation where the device detaches from the USB bus after the Ethernet
cable is disconnected. This is advantageous for mobile devices, as an attached USB device may
prevent the Host CPU from entering the APCI C3 state. Allowing the CPU to enter the C3 state
maximizes battery life, as the C3 state is the lowest of the four APCI power states.
When detached, the device is in a low power state. After the Ethernet cable is reconnected, or a
programmed GPIO pin asserts, the device automatically attaches to the USB bus. GPIO pin assertion
is supported so that this feature can be used with external PHY mode. In this case, the external PHY’s
link LED would be connected to a GPIO.
Ethernet
1
Remove Ethernet Cable
SMSC
LAN9500A/
LAN9500Ai
2
USB Electricals Detach
...ZZZ
3
Battery-powered Netbook PC
may enter C3 sleep mode
Figure 7.1 Device Detach
SMSC LAN950x Family
DATASHEET
45
Revision 1.1 (04-18-13)
SMSC [ SMSC CORPORATION ]
