ATMEGA8U2-AUR Atmel, ATMEGA8U2-AUR Datasheet - Page 37

• Manufacturer Part Number: ATMEGA8U2-AUR
• Description: MCU AVR 8K FLASH 16MHZ 32TQFP
• Manufacturer: Atmel
• Series: AVR® ATmegar

Specifications of ATMEGA8U2-AUR

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Size: 8KB (4K x 16)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-TQFP, 32-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Converters: -

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