AT90USB64/128
External 3.0V - 3.4V
Power Supply
UVCC
AVCC
DVCC
UCAP
1µF
VBUS
UDM
UDP
UVSS
UID
VBUS
D+
D-
UVSS
UID
XTAL1
XTAL2
AVSS
DVSS
External 5.0V
Power Supply
5V
UVCC
AVCC
DVCC
UCAP
1µF
UVCON
VBUS
UDM
UDP
UVSS
UID
VBUS
D+
D-
UVSS
UID
XTAL1
XTAL2
AVSS
DVSS
21.4 General Operating Modes
21.4.1
Introduction
After a hardware reset, the USB controller is disabled. When enabled, the USB controller has to
run the Device Controller or the Host Controller. This is performed using the ID detection.
• If the ID pin is not connected to ground, the ID bit is set by hardware (internal pull up on the
UID pad) and the USB Device controller is selected.
251
7593A–AVR–02/06