Operation If Gpion And Gpiox Are The Same Pin - Intel PXA27 Series Design Manual

'USB Client Controller
The configuration of using separate GPIOs for GPIOn and GPIOx lets the PXA27x processor enter
sleep or deep sleep mode with a USB cable connected or disconnected to the USB Client interface.
Before entering sleep or deep sleep mode, the software must read the GPIOn pin to determine if a
USB cable is connected or not.
If a USB cable is not detected, the software must:
•
Configure the GPIOx pin as an input to allow the USB D+ line to float.
•
Configure the GPIOn pin to detect a wake-up event.
The PXA27x processor is then put into sleep or deep sleep mode.
If a USB cable is detected, software must configure the GPIOx pin as an input to allow the USB
D+ line to float. This looks like a virtual disconnect to the host controller although the USB cable
remains physically attached to the PXA27x processor USB Client interface.
The PXA27x processor is then put into sleep or deep sleep mode.
When the PXA27x processor wakes-up, software must drive the GPIOx signal high pulling USB
D+ high indicating to the host controller that a fast USB client device has been (virtually)
connected.
12.4.1.2

Operation if GPIOn and GPIOx are the Same Pin

See Figure 12-3
detection.
Figure 12-3. Self-Powered Device when GPIOn and GPIOx are Same Pins
PXA27x
Processor
USB Client
Controller
II:12-4
for illustration of a self-powered USB Client device utilizing one GPIO signal for
GPIOn
0 Ohm
USBC_P
0 Ohm
USBC_N
Note 1: Some designs use the internal pull-up resistor.
3.3V 5V
1.5K
Board
Ohm
Ground
Note 1
®
Intel PXA27x Processor Family Design Guide
USB Client
Cable
Connector
1
VBUS (+5V)
4
GND
3
USB D+
2
USB D-
USBC_003_P2