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4-2 PXA250 and PXA210 Applications Processors Design Guide
USB Interface
detected. When an interrupt occurs, software must read the GPIOn pin to determine if the cable is
connected or not. GPIOn is 1 if the cable is connected or 0 if the cable is disconnected. If a USB
connect is detected, then software enables the UDC peripheral and drives a 1 onto the GPIOx pin to
indicate to the host PC a fast USB device is connected. If a USB disconnect is detected, then
software must configure the GPIOx pin as an input, configure the GPIOn pin to detect a wakeup
event, and then put the part into sleep mode.
Also, at any time, you may use software to put the part into sleep mode. Before entering sleep
mode, configure the GPIOx pin as an input to cause the UDC+ line to float. This looks like a
disconnect to the host PC. The device can then be put into sleep mode. When the device becomes
active, software must drive a 1 onto the GPIOx pin to indicate to the host PC a fast USB device has
been connected.
4.1.2 Operation if GPIOn and GPIOx are the Same Pin
Out of reset, GPIOn is configured as an input and configured to cause an interrupt whenever a
rising or falling edge is detected. When an interrupt occurs, software must read the GPIOn pin to
determine if the cable is connected or not. This pin is 1 if the cable is connected or 0 if the cable is
disconnected. If the USB cable is connected, then software must enable the UDC peripheral before
the host sends the first USB command. If the USB cable is not connected, then software must
configure the GPIOn pin to detect a wakeup event, and then put the part into sleep mode.
4.2 Bus Powered Device
The applications processor cannot support a bus powered device model. When the host sends a
suspend, the device is required to consume less than 500 uA (Section 7.2.3 of the USB spec version
1.1). The applications processor cannot limit its current consumption to 500 uA unless it enters
sleep mode. If it enters sleep mode, all USB registers are reset and it does not respond to its host-
assigned address.