5

7766FS–AVR–11/10

ATmega16/32U4

channels 10-bit ADC with optional differential input stage with programmable gain, an on-chip

calibrated temperature sensor, a programmable Watchdog Timer with Internal Oscillator, an SPI

serial port, IEEE std. 1149.1 compliant JTAG test interface, also used for accessing the On-chip

Debug system and programming and six software selectable power saving modes. The Idle

mode stops the CPU while allowing the SRAM, Timer/Counters, SPI port, and interrupt system

to continue functioning. The Power-down mode saves the register contents but freezes the

Oscillator, disabling all other chip functions until the next interrupt or Hardware Reset. The ADC

Noise Reduction mode stops the CPU and all I/O modules except ADC, to minimize switching

noise during ADC conversions. In Standby mode, the Crystal/Resonator Oscillator is running

while the rest of the device is sleeping. This allows very fast start-up combined with low power

consumption.

The device is manufactured using ATMEL’s high-density nonvolatile memory technology. The

On-chip ISP Flash allows the program memory to be reprogrammed in-system through an SPI

serial interface, by a conventional nonvolatile memory programmer, or by an On-chip Boot pro-

gram running on the AVR core. The boot program can use any interface to download the

application program in the application Flash memory. Software in the Boot Flash section will

continue to run while the Application Flash section is updated, providing true Read-While-Write

operation. By combining an 8-bit RISC CPU with In-System Self-Programmable Flash on a

monolithic chip, the ATMEL ATmega16U4/ATmega32U4 is a powerful microcontroller that pro-

vides a highly flexible and cost effective solution to many embedded control applications.

The ATmega16U4/ATmega32U4 AVR is supported with a full suite of program and system

development tools including: C compilers, macro assemblers, program debugger/simulators, in-

circuit emulators, and evaluation kits.

2.2

Pin Descriptions

2.2.1

VCC

Digital supply voltage.

2.2.2

GND

Ground.

2.2.3

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 has better driving capabilities than the other ports.

Port B also serves the functions of various special features of the ATmega16U4/ATmega32U4

as listed on page 72.

2.2.4

Port C (PC7,PC6)

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.