ATMEGA8U2_14 Datasheet, PDF (194/310 Pages) ATMEL Corporation – 125 Powerful Instructions – Most Single Clock Cycle Execution

ATmega8U2/16U2/32U2
SUSPI
Suspend detected = USB pad power down _{Clear Suspend by software}
WAKEUPI
PAD status
Resume = USB pad wake-up
Clear Resume by software
Active
Power Down
Active
Moreover, the pad can also be put in the Idle mode if the DETACH bit is set. It come back in the
Active mode when the DETACH bit is cleared.
20.8
D+/D- Read/write
The level of D+ and D- can be read and written using the UPOE register. The USB controller has
to be enabled to write a value. For read operation, the USB controller can be enabled or
disabled.
20.9
USB Software Operating modes
Depending on the USB operating mode, the software should perform some of the following
operations:
Power On the USB interface
• Configure PLL interface
• Enable PLL
• Check PLL lock
• Enable USB interface
• Configure USB interface (USB Endpoint 0 configuration)
• Attach USB device
Power Off the USB interface
• Detach USB device
• Disable USB interface
• Disable PLL
Suspending the USB interface
• Clear Suspend Bit
• Set USB suspend clock
• Disable PLL
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