ATmega16U2 Atmel Corporation, ATmega16U2 Datasheet - Page 27

• Manufacturer Part Number: ATmega16U2
• Manufacturer: Atmel Corporation

Specifications of ATmega16U2

• Flash (kbytes): 16 Kbytes
• Pin Count: 32
• Max. Operating Frequency: 16 MHz
• Cpu: 8-bit AVR
• # Of Touch Channels: 12
• Hardware Qtouch Acquisition: No
• Max I/o Pins: 22
• Ext Interrupts: 21
• Usb Transceiver: 1
• Usb Speed: Full Speed
• Usb Interface: Device
• Spi: 2
• Uart: 1
• Graphic Lcd: No
• Video Decoder: No
• Camera Interface: No
• Analog Comparators: 1
• Resistive Touch Screen: No
• Temp. Sensor: No
• Crypto Engine: No
• Sram (kbytes): 0.5
• Eeprom (bytes): 512
• Self Program Memory: YES
• Dram Memory: No
• Nand Interface: No
• Picopower: No
• Temp. Range (deg C): -40 to 85
• I/o Supply Class: 2.7 to 5.5
• Operating Voltage (vcc): 2.7 to 5.5
• Fpu: No
• Mpu / Mmu: no / no
• Timers: 2
• Output Compare Channels: 5
• Input Capture Channels: 1
• Pwm Channels: 4
• 32khz Rtc: No
• Calibrated Rc Oscillator: Yes

8.1.4
8.2
8.2.1
7799D–AVR–11/10
USB
CPU Clock
External
Oscillator
RC oscillator
Clock Switch
USB Clock – clk
Exemple of use
non-Idle
The USB is provided with a dedicated clock domain. This clock is generated with an on-chip PLL
running at 48 MHz. The PLL always multiply its input frequency by 6. Thus the PLL clock register
should be programmed by software to generate a 8 MHz clock on the PLL input.
In the ATmega8U2/16U2/32U2 product, the Clock Multiplexer and the System Clock Prescaler
can be modified by software.
The modification can occur when the device enters in USB Suspend mode. It then switches from
External Clock to Calibrated RC Oscillator in order to reduce consumption. In such a configura-
tion, the External Clock is disabled.
The firmware can use the watchdog timer to be woken-up from power-down in order to check if
there is an event on the application.
If an event occurs on the application or if the USB controller signals a non-idle state on the USB
line (Resume for example), the firmware switches the Clock Multiplexer from the Calibrated RC
Oscillator to the External Clock.
Figure 8-2.
USB
Ext
3ms
Idle
Example of clock switching with wake-up from USB Host
Watchdog wake-up
from power-down
(Suspend)
1 Resume from Host
RC
ATmega8U2/16U2/32U2
1
resume
non-Idle
Ext
27