5
7707A–AVR–03/07
AT90USB82/162
Pin Descriptions
VCC
Digital supply voltage.
GND
Ground.
Port B (PB7..PB0)
Port B is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port B output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port B pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port B pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port B also serves the functions of various special features of the AT90USB82/162 as listed on
Port C (PC7..PC0)
Port C is an 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The
Port C output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port C pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port C pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
Port C also serves the functions of various special features of the AT90USB82/162 as listed on
Port D (PD7..PD0)
Port D serves as analog inputs to the analog comparator.
Port D also serves as an 8-bit bi-directional I/O port, if the analog comparator is not used (con-
cerns PD2/PD1 pins). Port pins can provide internal pull-up resistors (selected for each bit). The
Port D output buffers have symmetrical drive characteristics with both high sink and source
capability. As inputs, Port D pins that are externally pulled low will source current if the pull-up
resistors are activated. The Port D pins are tri-stated when a reset condition becomes active,
even if the clock is not running.
D-/SDATA
USB Full Speed Negative Data Upstream Port / Data port for PS/2
D+/SCK
USB Full Speed Positive Data Upstream Port / Clock port for PS/2
UGND
USB Ground.
UVCC
USB Pads Internal Regulator Input supply voltage.
UCAP
USB Pads Internal Regulator Output supply voltage. Should be connected to an external capac-
itor (1F).
RESET/PC1/dW
Reset input. A low level on this pin for longer than the minimum pulse length will generate a
reset, even if the clock is not running. The minimum pulse length is given in
Table 15 on page47. Shorter pulses are not guaranteed to generate a reset. This pin alternatively serves as
debugWire channel or as generic I/O.
XTAL1
Input to the inverting Oscillator amplifier and input to the internal clock operating circuit.
XTAL2/PC0
Output from the inverting Oscillator amplifier if enabled by Fuse. Also serves as a generic I/O.