ATmega16U2 Atmel Corporation, ATmega16U2 Datasheet - Page 37

• 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

8.11
8.11.1
7799D–AVR–11/10
Register Description
CLKSEL0 – Clock Selection Register 0
Figure 8-6.
• Bit 7:6 – RCSUT[1:0]: SUT for RC oscillator
These 2 bits are the SUT value for the RC Oscillator. If the RC oscillator is selected by fuse bits,
the SUT fuse are copied into these bits. A firmware change will not have any effect because this
additionnal start-up time is only used after a reset and not after a clock switch.
• Bit 5:4 – EXSUT[1:0]: SUT for External Oscillator / Low Power Oscillator
These 2 bits are the SUT value for the External Oscillator / Low Power Oscillator. If the External
oscillator / Low Power Oscillator is selected by fuse bits, the SUT fuse are copyed into these
bits. The firmware can modify these bits by writing a new value. This value will be used at the
next start of the External Oscillator / Low Power Oscillator.
• Bit 3 – RCE: Enable RC Oscillator
The RCE bit must be written to logic one to enable the RC Oscillator. The RCE bit must be writ-
ten to logic zero to disable the RC Oscillator.
• Bit 2 – EXTE: Enable External Oscillator / Low Power Oscillator
The OSCE bit must be written to logic one to enable External Oscillator / Low Power Oscillator.
The OSCE bit must be written to logic zero to disable the External Oscillator / Low Power
Oscillator.
• Bit 0 – CLKS: Clock Selector
The CLKS bit must be written to logic one to select the External Oscillator / Low Power Oscillator
as CPU clock. The CLKS bit must be written to logic zero to select the RC Oscillator as CPU
clock. After a reset, the CLKS bit is set by hardware if the External Oscillator / Low Power Oscil-
XTAL1
XTAL2
Bit
(0xD0)
Read/Write
Initial Value
RC OSCILLATOR
8 MHz
OSCILLATOR
XTAL
PLL Clocking System
RCSUT1
R/W
7
0
RCSUT0
R/W
6
0
CKSEL3:0
EXSUT1
R/W
5
0
To System
Clock Prescaler
PLL clock
Prescaler
PINDIV
EXSUT0
R/W
4
0
clk
8MHz
ATmega8U2/16U2/32U2
PLOCK
RCE
R/W
3
Detector
Lock
PDIV3..0
PLL
PLLE
See Bit Description
EXTE
R/W
2
/48
T1
/2
R
1
-
PLLITM
PLLUSB
1
CLKS
0
1
0
R/W
0
Tclk Timer1
clk USB
CLKSEL0
37